I see a lot of people expecting Xenoblade 3. Kojima/Takahashi actually hinted that they want to take a different approach this time around. My guess is either a sequel to Xenoblade X or a new Xenoblade universe.
I did say they could be making a new Xenoblade universe, which could be any sort of setting.
Regarding the other part, XC2 is pretty different from XCX in terms of tones, setting, plot and world structure. I don't understand what you mean by it not being different enough?
A new Xenoblade universe could still be called Xenoblade 3. I expect a Xenoblade 3 that has nothing or not much to do with Xeno 1/Xeno 2. The games don't have to have direct connections imo and the next Xenoblade could have a totally different setting and still be called Xenoblade 3 (he said he wanted to go forward with the numbering at some point). Of course they could make a Xenoblade X 2, but with the storydriven Xenoblade 2 being the bigger success i would think they will go that way again, but perhaps with a bigger open world. In the end we know nothing and have to wait lol.