Yeah I see Metroid making a comeback. 2D Metroid, MPT and MP4 in the next 3 years.
And hopefully it becomes a consistent series where it can get spinoffs due to the main series being successful.
It'd be great to see the series have a 'Breath of the Wild' moment - not just where it gets the kind of universal acclaim Metroid hasn't really had since Metroid Prime launched back in 2002, but were it breaks out of the sales rut the series has always been stuck in. Obviously we don't know yet how sustained Zelda's success will be, but Link's Awakening strong launch bodes well, as do BotW's ongoing strong sales. Be fascinating to see what shipments are when the quarterly results come out tomorrow. For a series than often sold in the 3 to 5 million range, with a few entries in the 6 to 8 million range, Breath of the Wild's 15 million and counting is an incredible success for Zelda.
I'm really not sure how much head-room there is for Metroid. The normal sales range seems to be somewhere around 700k to 1.5 million, with only Prime and the original managing more than that, with both games coming close to the 3 million mark. If we get a scenario where major Metroid titles (like the next 2D entry and Prime 4) can be relied on to sell in the 3 million or more range, and where spin-offs can reliably sell 1 million or more, then that's actually a stronger commercial position than the franchise has historically had - where Nintendo can't even bank on a Metroid title breaking the million mark, or getting beyond 1.5 million (which neither Super Metroid or Prime 3 managed, for example).
If we or Nintendo wanted Metroid to break out like BotW did, it'd need an entry that sells somewhere between 3 and 5 times the normal sales range, or twice as much as the previous best-selling entries. That'd put a ballpark figure total of 3 million at the lower-end, up to 6 million at the top end. That top end figure is a huge ask, though I think, if the stars align, we could finally see Metroid break the 3 million mark on Switch.