After reading some of the recent patent applications, I think we're going to see
1) simplified carbs appear in next gen strato engines. A lot of patents apply to doing away with dual-barrel carbs, for cost, complexity, size, weight.
2) lighter saws. Simpler carbs mean a little less weight.
Here is a summary of some of the patents I've read.
http://www.freshpatents.com/-dt20090514ptan20090119934.php
May 2009 - Auto chain tensioner.
This sounds a lot like the keyless tensioner found on the 450e series, where the side cover and chain tension are in a single mechanism.
http://www.freshpatents.com/-dt20100408ptan20100083512.php
April 2010 - Chain Saw
Bunch of stuff. Dual-port muffler in case one port is clogged. Partially covering the muffler on small saws with a plastic cover. A pipe coming off the muffler where the hot gases escape, and the pipe has a slit/holes in it to allow a venturi with cool air, so that the ejected gases are not as hot, avoiding discoloration of plastic on the saw.
http://www.freshpatents.com/-dt20100408ptan20100083511.php
April 2010 - Chain Saw
Attempts to overcome reduction in airflow when the openings of the side cover are clogged by i) having windows around the mounting hole of the flywheel, ii) making a larger flywheel (which won't increase the weight since the windows remove some weight), and iii) having cooling veins on the backside of the flywheel to increase airflow.
http://www.freshpatents.com/-dt20100701ptan20100163337.php
July 2010 - Muffler
Smaller lighter saws have smaller mufflers made of thinner metal, that don't last when exposed to hot exhaust gases, so baffles are used, which requires spot welding... But on smaller mufflers welding baffles is difficult and expensive and time consuming, so they propose bending a tab into the path of the exhaust gases inside the muffler so that they can create smaller, cheaper mufflers out of thinner metal.
Note to future self : consider NOT removing this tab if I want my muffler to last.
http://www.freshpatents.com/-dt20101118ptan20100288251.php
November 2010 - Scavenging cover
Since the diameter of the ports in the cylinder affect airflow, optimizing the port size is difficult across different model saws, with a lot of re-casting and trial-and error. Of note, they aren't optimizing for power, they are optimizing to minimize blow-back. So instead they suggest using a replaceable cover between the carb and the cylinder with a window of varying sizes that they can swap in and out to optimize flow for different model saws. Porting gurus rejoice!
http://www.freshpatents.com/-dt20101125ptan20100294249.php
November 2010 - Insulator
Husqvarna is aware of a problem with strato-engines where they run very lean at idle, and off idle they get leaner, can hesitate, choke or die.
A commonly available engine including the stratified scavenging two-cycle engine is typically driven with lean mixture during idling. However, when the stratified scavenging two-cycle engine is suddenly accelerated from an idling state, air from the air passage is initially supplied into the cylinder and therefore mixture having a predetermined fuel ratio, which follows the air, is not sufficiently supplied. Consequently, the lean mixture becomes further lean, which causes acceleration failure or engine stop.
So they propose an accelerator pump to inject fuel and overcome this problem. Accelerator pumps in the carb are not new, so this one is integrated with the heat insulator boot between the cylinder and the carb in the dead space to reduce space used by the accelerator pump.
http://www.freshpatents.com/-dt20120614ptan20120146249.php
June 2012 - Carburetor
In the dual-barrel carb of strato engines, the carb is very large, and the passage is long(er than regular chainsaw carbs). So they suggest using a venturi (a bulge in the airpath) to accelerate the air through the carb in the air-only side, and making a shorter barrel carb.
http://www.freshpatents.com/-dt20120719ptan20120180769.php
July 2012 - Two-Cycle Engine
Offset counterweights on the con.rod to reduce vibration and improve engine efficiency. This one looks juicy, but says very little.
http://www.freshpatents.com/-dt20120920ptan20120234304.php
September 2012 - Stratified-Scavenging Two-cycle Engine
Does away with a dual-barrel carb in strato engines for a simpler single-barrel carb. They suggest that the insulator between the carb and the cylinder has two windows for the air-fuel mixture and the scavenging port, and the jet in the carb is movable. Airflow through the carb through the lower fuel-mixture port creates negative pressure and pulls the jet up and allows fuel to spray into the airstream. Airflow through the carb going through the upper scavenging port doesn't create enough negative pressure around the jet, and it falls down, not spraying fuel into the air stream.
http://www.freshpatents.com/-dt20120927ptan20120240907.php
September 2012 - Stratified-Scavenging Two-cycle Engine and carburetor
Much like the previous patent, just with some wording changes and clarification, and explaining it in conjunction with the strato engine.
http://www.freshpatents.com/-dt20130425ptan20130098325.php
April 2013 - Air Supply Device for 2 Stroke Engine
Blow-back normally causes increased emissions and lower fuel economy by blowing air and fuel back through the carb into the air filter. This solves the problem without preventative plates or reed valves by creating an accumulator that catches the fuel inside the air filter housing, and a passage takes it directly into the crank case body to be used.
http://www.freshpatents.com/-dt20130829ptan20130220260.php
August 2013 - Air Supply Apparatus for Two-Stroke Engine
If using a single-barrel carb with a strata-engine, there may be mixing of fuel in the air-only scavenging airstream. So, they design an air filter housing with two discharge ports to efficiently direct airstreams into the carb.
http://www.freshpatents.com/-dt20130905ptan20130228152.php
September 2013 - Air Supply Device of Stratified Scavenging Two-Cycle Engine
Expounding on the previous patent with pictures and further clarification. Goes on to describe flow rate regulators and their design.
http://www.freshpatents.com/-dt20131107ptan20130291840.php
November 2013 - Stratified Scavenging Two-Stroke Engine
Little confused on this one, not sure if they are talking about the scavenging port, or the transfer ports. In current scavenging engines the amount of air chased through the cylinder is controlled by the port size in the cylinder. The transfer size is defined by a transfer cover, and a partition in the transfer cover. The transfer port is low, close to the case, and to make a cheaper interchangeable lineup of saws, a single crankcase design could mate with the same cylinder and the cylinder would partly determine the port size by using the skirt on the cylinder as a flow restrictor in combination with the different transfer covers.
2014 - no updates
2015 - no updates