I don't think too many of the parts will interchange. Certainly not the internal stuff. External parts like the starter and side cover maybe? Like Tor says, have to study the IPL's. Which I can now thanks to him! They are still not available on the US dealer site.
Then you have to look at some costs here. Even if the newer parts will fit, they will start to add up quick. And changing one part, may require additional changes. Want the new air filter? Going to need the new filter holder, as well as the top cover cause the new filter won't fit under the old cover. Really it's more of an all new saw than updates to the original. And this is why 552XP would have been a better idea: I need a blah, blah, blah for a Husky 550. Which one? I Don't know.
Red Max won't be getting any of these new saw models until they show some signs of selling what they already have in the catalog. And that's not happening by any stretch.