Microsoft won't be releasing an XB2. They will claim that XB1X was their next gen console, while slowly retreating from the console market. Why?
1. After 4K 30 FPS there's not much you can do as far as graphics go without breaking the bank. Playing Witcher 3 in 4K takes a $1000 PC for 30 FPS. Playing Witcher 3 in 4K at 60 FPS takes well over $3000. A few years won't change this fact enough to make a $500 console that can play games at 4K 60 FPS feasible. Graphics won't surpass Witcher 3 on ultra setting, because that level of detail is too labor intensive for most studios. This is why only CDPR, and Sony have been able to push the envelope this gen. Only they have the money and talent to get over the labor hump.
2. PC gaming is becoming more popular than ever. MS already makes money on Windows, so why would they bother staying in the console market, when they think it will end within another generation or two? MS's intent with Xbox was to defend the PC from the livingroom space. They seem to think they've accomplished that.
3. MS's biggest moneymaker is XBL, not XB1. As long as they can successfully hold onto their XBL customers they are going to do a slow 7 year phase out of XB consoles as a whole, switching over to games as a service.
4. Sony is crushing them this gen, and it's blatantly obvious that MS cannot compete with them.
This is where I think MS is headed too. They're already trying to prep customers with the "generations are dead" propaganda.
To elaborate on your point 4, I don't think MS can compete in the console space without Buying marketshare; that is how they did it with XBox and XBox 360