While there were attempted joint-efforts with Nintendo between Microsoft & Sony, those never panned out with Nintendo... which happened to spawn the PlayStation (as it was originally a joint project to add CD-ROM to the SNES before Nintendo changed partners & ultimately dropping the project). While I haven't heard any hard joint-efforts with Microsoft & Nintendo, they are practically neighbors (while their US HQ's are around 10 blocks or so apart, based on Google Maps, buildings between Nintendo & Microsoft are a bit intermingled) & there was likely some cross-over with the sale of their controlling stake of Rare (from Nintendo, to Microsoft).
Fiscally, neither company has the funds to completely buy out Nintendo (while unconfirmed, rumors have it that Nintendo could go for 20 years without profitability with their liquid assets). Nintendo really does have any need (beyond investor pressures) to consider going purely 3rd party, although they are slowly evolving to be a bit more flexible as they start amassing a gaming presence on mobile phones (which is competing with their mobile gaming consoles).
Unless Nintendo & their executives commit massive blunders & have a long line of consecutive market failures (nobody & no company is perfect), its unlikely that conditions will change.