Soundwave on 11 April 2016
There's a conspcious three year gap from LM to Metroid Prime Federation Force, I don't think they've been working on FF all this time.
Luigi's Mansion 3 probably started development some time soon after 2013's LM launch on 3DS where the game turned out to be a bigger than expected hit. That's pretty much standard operating procedure for Nintendo with successful Western games -- a sequel is immediately greenlit (see also: Donkey Kong Country: Tropical Freeze).
My guess is sometime around 2014, Nintendo moved Luigi's Mansion 3 away from the Wii U and to the NX and within that downtime, Federation Force was pushed to the forefront.
