He also wore those pins some years ago. Didn't mean a thing.
What if the pins did mean something? What if there were plans to release a Metroid game on WiiU, but Nintendo decided to save it for Switch. I've maintained that it isn't out of the realm of possibility that Retro is codeveloping MP4 with Bandai-Namco, particularly if MP4 does to the Prime series what both Mario Odyssey and Breath of the wild did for 3D Mario and 3D Zelda.
I for one would love some open room to shinespark in, wouldn't you? And to truly space jump/screw attack across vast distances.
This would explain Retro's lack of anything at the last few E3s outside of Donkey Kong.
I know this is all conjecture and not based in fact, but at this point it isn't like there are many facts to go by anyway. I mean look at us, we're speculating about a shirt in a picture of Reggie. But it sure is fun!