That is an even worse scenario.
When MS advertised Grabbed by the Ghoulies with "From the Creators of Donkey Kong Country," DKC GBA sales went up. Now of course, GBTG tanked pretty hard, but they found they could not advertise Rare at all without mentioning their past.
This is where they run into a problem with Sakaguchi. I don't know if they can find a way to advertise his stuff without mentioning he created Final Fantasy and advertising FF for their competition at the same time.
JSRF is like a hundred times less niche than Rez. Everything that Rez guy has been involved with has been a complete failure, and this was on the PS2. Please Note I am not talking about his game quality, this is strictly sales. I doubt this will help MS out very much.
And while I try not to speak ill of some developers, I can't remeber the last game Okamoto directed. I think it was Street Fighter 3: Third Strike, and before that I think it was a GBC Zelda or something. I also can't think of a game he made under his new company. So they are largely untested. This is probably their largest asset in these acquisitions, mostly because of not knowing what to expect.