Yes, MS bought out rare. The offered nintendo the chance 1st, but Nintendo declined.. MS picked them up right away.
Rumor has it that many of the Goldeneye/Perfect Dark creators & team members disbanded from Rare... and started this company called Zoonami based out of the UK. <a href="http://www.zoonami.com/" target="_blank">http://www.zoonami.com/</a>
They are creating games soon for the Gamecube, one is called game Zero.. you can see some of the stuff on that webpage. Its small, but very interesting

... Maybe this is Why Nintendo let Rare go?
Back to GCN online games. They are not "concentrating" but they will have more for the Gamecube. Its just a matter of time before they come out. It has been kept somewhat quiet... and I am not sure why.
Expect Animal Crossing 2 and Mario Kart to be fully only..... more 1st party games should be online too.. and I know some 3rd party RPG's ..etc... are in the works for online on the GCN... I just don't have enough info about it right now.
†B†V†