I hope they come back someday.
You see the thing is with Rare is you can never guess what they're going to do next. Whenever you get your hopes with Rare you always end up dissapointed - but then they come up with some suprise announcement in the most unlikely of places and everything is wonderful (if that makes sence). They're mysterious because you never know.
When Rare got bought out by micro$oft they had been going for 20 years - but they'd only been owned by Nintendo for 8 years. Look at the bigger picture - and you can see that the time with Nintendo was just 1 chapter of the Rare story, and now with micro$oft - its just yet another chapter - and the'll be many more to come I'm sure. Because they're a great developer - commited to making the best games possible - they always will be no matter what happens to them in the future.
And they haven't left Nintendo completely - since they've been with micro$oft they've worked with Nintendo to update Donkey Kong Country 1 and 2 for GBA and possibly they're working on DKC3 - but as I said, you never know with Rare. They are the leading *number 1* developer (in my view) for GBA - making extremely high-quality games and really setting the standard for others to follow. And I'm pretty sure they'll make games for Nintendo DS although nothing is confirmed. Micro$oft (purely out of choice) are giving them full decision-making freedom - so they won't ever be forced to become less dedicated to GBA and DS.
So, yeah, its a shame about no GC support but... those poor xbox owners have to have *something*.