Yes, Mint is not a 1 DE distro. Gnome will likely continue to be the main DE either with both Cinnamon and MATE or with one of them.
I think Ubuntu's Unity and Mint's MATE/Cinnamon are just the first steps in a process that will ultimately lead to a breakup with Gnome. When few years from now Gnome deprecating handy desktop features because they don't work with a touch interface have left traditionalist distros little choice but to either fork or leave Gnome, at that point I hope Ubuntu, Mint (and Pinguy and the whole Ubuntu branch) will come together and maintain a Gnome fork. They can't continue to patch over Gnome's touch pipe dreams, especially not Mint.
Thank you for this thread. That’s all I can say. You most definitely have made this forum into something special. You clearly know what you are doing, you’ve covered so many bases. Thanks!