It's only a way to spur interest in their investment. If Sony wants to retain gamers in their ecosystem by releasing a more powerful version of their PS4, MS doesn't care if people migrates to PC or not. What we have here is two different approaches. They will hop on the 4K bandwagon because they don't want to be left behind, they will also hop on the VR bandwagon, on the game streaming bandwagon just like they hopped on the gesture controller bandwagon.
Create interest in their consoles by using newer technology available is imo the reason they create these mid gen consoles. If Sony didn't want people to migrate to PC they wouldn't release PSNow with PS4 games on PC. Same as MS wouldn't come up with the Play Anywhere program.