The only reason I want rare back with Nintendo is because of Banjo, and I imagine Nintendo would fully support a 3D platformer Banjo-Kazooie. Even if Rare isn't the developer, I'm sure there are plenty of people who are capable of making a good Banjo game.
Believe me, I was there when gamestop opened for Banjo-Kazooie Nuts & Bolts, and the employee looked at me like I was retarded and said, "You know, the shipment doesn't come in until noon... so come back later...". The game is good but a huge departure from the rest of the series, and not what I would have preferred.
Banjo-Threeie is up there with Mega Man Legends 3, Chrono Break, and even Shenmue 3 for my most wanted games. If Nintendo can make it happen then I would be all for it. Of course, I've been talking as if this rumor isn't complete shit but whatever, :P
I'm not so much concerned about Rare but their IPs... and really only Banjo.