While I think Platinum Games would do a good job on Star Fox, it dosen't seem logical in my opinion.
Why would Nintendo allow a third party developer to work on a first party game? Nintendo will probably be able to make a Star Fox game cheaper and faster with the experts who've made all the previous games.
Not to mention Platinum Games can make their own game with a similar style to Star Fox, yet it can be a different IP; which I feel would accomplish the same goal, and that IP would belong to Platinum Games, not Nintendo.