There is zero official indication Nintendo plans to reacquire Rare Ltd. (acquired by Microsoft in 2002 for $375M). Here's a strategic breakdown.
Nintendo frequently co-develops with external partners: Mario + Rabbids (Ubisoft), Metroid Dread (MercurySteam), Pikmin 4 (Eighting), Fire Emblem Engage (Intelligent Systems/Koei Tecmo). A Rare/Nintendo co-pro (e.g., Banjo in Smash DLC style) is plausible. Full buyback: near zero.