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Some of the problem with these guesses is that they lack education on who is actually working at Retro Studios. The majority of whom have only experience in linear platformers, their last one requiring 4 years of development. Making the jump to an open world Star Wars game, with only 3-4 years dev time, makes about as much sense as the Kirby's Dreamland 3 team reassembling to develop Final Fantasy 15.
And before using the "Nintendo did Zelda in one try" argument. No they didn't! Nintendo worked with Retro studios, who had been developing pacing in large scale 3D games for a decade and a half, and had been working on open world design for at least a decade. In addition, the Zelda team had always been working on elements that work well within an open world environment. Lastly, the Zelda team developed Link Between Worlds, released in 2013, as a bit of a prototype for the Zelda universe, as well as a Zelda-1 based open world prototype. Throw on top of everything that the Breath of the Wild design team is one of the most talented and experienced video game design teams in history, and were incredibly detailed in their research and prototyping.
Most of the original Metroid Prime staff has left and are largely spread out between Warner Bros, Activision/Blizzard, Valve, Electronic Arts, Microsoft, and Sucker Punch. Current Retro Studios staff is largely young in the industry, and have all their familiarity with the two DKC clones, which is all they released in the last decade. I don't think Retro Studios has experience or staff capacity to develop an open world game. Their whole purpose is to update old ideas.
If they're doing something with the Metroid license, don't expect an open world game, expect a 2D Metroid title with some elements from the latest DKC title they released. That would be the only logical direction for them with that franchise. Next, they could potentially be doing a Kart racing game, Diddy Kong Racing?
I describe myself as a little dose of toxic masculinity.
