Honestly, I don't want any third party company working on Prime 4. Or at least being the primary developer for it.
I just want Metroid to have a dedicated team for it just like how it did from the 80s to the early 2000s. All the 2D Metroids prior to Samus Returns were developed by R&D1, but after Zero Mission, that division disbanded and its staff either retired or were transferred to EAD or SPD (where Sakamoto went). After Retro finished their trilogy and moved on to Donkey Kong Country, Metroid had no proper team to back it up like how series like Animal Crossing and Zelda do.
It's pretty telling that Sakamoto has to keep bringing in outside companies like Team Ninja or MercurySteam to help him make more Metroid titles. So in that case, I hope, by "a new, talented development team", they mean an all new division at EPD full of fresh blood dedicated to making new Metroid games.