I'm not sure what the "software" companies would gain from buying Canon or Leica that they don't already have.
That said, you're also dismissing one of the biggest value propositions camera companies have, which is decades of physical user interface experience and developed hardware modularity. Phones absolutely do not replace good cameras for usability.
When travelling I take a mix of photos between my phone and camera, and when I need my camera it's irreplaceable, and when I don't need my camera, I use my phone. The phone is quick and easy, but the camera makes me a photo ninja and I get specifically configured shots quickly in a way I could never replicate with a phone interface.