The cancellation of Raven Blade is what made Retro the studio they are today. It allowed them to focus 100% on Metroid Prime, the game that put them on the map.
People lost their shit when Donkey Kong Country Returns was announced. I mean vast amounts of the gaming populace were unable to locate their excrement for weeks. That was an awesome moment for Nintendo and for Retro. Nowadays it's "ho hum another 2D platformer," apparently it's easy to forget how excited people were for some new Donkey Kong Country after getting 2 Metroid games per platform for 4 consecutive platforms.
Making Tropical Freeze was Retro's decision. They had a lot of ideas left over from the development of Returns that they didn't have a chance to implement in that game. And not everyone who worked on the Prime games is still at Retro; even though I'm sure they could handle it because they're a great studio, who knows whether the devs there actually want to make Metroid or not.
Also it's far too late for the Wii U to drastically change its course at this point, no matter what Retro does.
