I don't think it would be a bad move to cautiously buy a 346 in the months leading up to its replacement. It seems that husky has its game down now, has figured out how to make strato saws that are light, slim and lightening fast, and so presumably the 550xp will be a great (and perhaps better saw).
The 346 xp NE is a "just right" saw to me. There really isn't anything I would change on it. There's potential that the 550xp could be more "just right" and there's also potential for it to be a little bit off.
I have the highest hopes, and don't doubt husqvarna one bit, but it's kind of like an musicians best song or best album--at one very moment, they were just right in the zone of where they needed to be, and everything came together perfectly--and the result is perfect like the stars.
The price tag of the 550xp is probably going to be a bit scary too. i think we can think lists of $550+ here in the US in the trends with the 555 and 560/562 price increases are continued.
I think that these prices aren't going to make it impossible for guys to buy saws. I think it will just mean a little bit less hoarding for most of us, slimmer fleets, etc. I'm not saying I'm in favor of price increases, but they shouldn't be the complete end of the world. To rant a bit more, I feel like some of these price increases are justified, in that the saws have more technology in them and components which would certainly cost more to include.