I think a buyout by Nintendo, Sony, or Microsoft would be bad.
Sony would take away some of the support that nintendo so desperately needs from some of capcoms games
microsoft has no handheld and their lack of focus on the Japanese game market would mean then end of numerous franchises
And nintendo could potentially end some franchises that didn't match their target demographic or change them. If one of the three had to buy them I'd personally prefer Sony or Nintendo, but I think a strong third party company would be the best option since then the titles could stay matched with the platforms they currently are available on.
I am not sure I would be any kind of worked up about the Sony one. Nintendo seems to be the games equivalent of film remakes right now -- sometimes good but generally it does not mean your earlier memories are now somehow invalid.
Microsoft has no handheld? Did I miss the part where they had a slightly struggling tablet and phone OS? Also the part where they published games on Nintendo's handhelds for quite some time before then. Likewise would it mean the end of things in the Japanese market if buying such a company was the way into the Japanese market?
I already went on Nintendo and the above probably says just as much again.