All at the same time unrealistic, but not if it's only one of them. I could definitely see Sony trying to get Square or Sega. Both have synergies in common.
Square is a really bad purchase. I know why people keep bringing it up, but it makes really very little sense for Sony. Sony already has quite a few Square games exclusive and they're not performing overly well at that. What exactly do they gain by buying Square Enix right now?
That just maintains the status quo and doesn't really sell more PlayStation consoles or improve their software lineup. Doesn't massively improve their PC strategy either. Probably helps most with Mobile.
CDPR, Capcom, Sega, are all better buys.