I could see maybe a collaboration to help Capcom work but I
definitely don't think Nintendo buying the franchise would be a good move considering their history with their own IPs. As opposed to Mega's 3-5.5 year current abscence:
was shelved for the entire N64 era and its latest game was around 5 years ago, which didn't sell as much as Nintendo wanted and was pretty controversial for a lot of reasons (mainly Samus' characterization and the horible story). They did give us Federation Force at E3, but not too many people were happy about it.
has been asleep since 2004, as Nintendo is still struggling to find a way to make the game feel new again (as Miyamoto said in an interview about a few years back iirc)
only got one game for the entire Wii & DS era and only recently came with Star Fox Zero after nearly a decade
had a 15 year wait to get Punch Out for Wii, and THAT game was also around 5 or 6 years ago.
had a whopping 25 year wait for his game before Sakurai brought him back in Brawl and then making Uprising. Even now, Sakurai says he doesn't plan to make a sequel and that we'll likely have to wait yet another 25 years for a new K (I'm not sure if it really will end up that way, but ya never know)
Honestly, unless its
or maybe
, Nintendo's had a history of ignoring their franchises for just as long, sometimes even longer than 3-5 years. They pay attention to sales numbers just as much, if not more than Capcom does (they were gonna cancel Fire Emblem and make Awakening its last game for instance because of the series' poor sales, if it wasn't for its high sales it'd probably be dead by now) and they might not be the saving grace for MM people think it is. We wouldn't know unless it actually happened: They could shelf him again for all we know, or best case scenario could be that they make a few MM games and then ignore him again. They already have trouble managing their own IPs and own too many they have to worry about, so I don't think its in their best interest to start worrying about those of other companies. Not to mention that if they got the IP they would have to give said franchises even less attention, they only have so much time, money, resources, and employees to work with after all.
I also love peoples' assumption that Nintendo even
wants to make MM games just because he's in Smash. Iirc the only other time Nintendo really got involved was them publishing Mega Man 6 in North America (as Capcom didn't feel like it due to a declining support for the NES). Nintendo is a great company but, until I see Capcom make him a cash cow again or worse, I feel Mega Man is at home where he is, its just not worth it imo.
Also, my personal message to the people wanting Nintendo to buy Mega Man: Even if Nintendo did want the rights to it, Capcom has not, nor will they ever even consider selling the Mega Man IP. Like it or not, it is still a very important franchise to them and the series needs focus from all the countless games he's already got, and it just doesn't finish in a mere few years. Its almost like Disney giving away Mickey Mouse, its just not gonna happen.