I doubt they will just keep doing partial upgrades. I think they'll try at least 1 new console that's full backwards compatible.
Well the power increase is practiically like a next gen console. It takes a lot of power to make the jump from 720p-1080p to 4K. Some developers will opt to use much of that power on graphics/performance instead and those titles will look a generation ahead of current consoles.
Just because they keep calling it X1 doesn't mean that limites the potential upgrades on specs. But at some point high end games will have to stop supporting 1st gen specs, kinda like phones. But more simplistic stuff like indie games, classic ports, could support 1st gen X1 for many years. Atleast I would hope that's the direction MS is going with X1.
Hence, its like the PC. They don't move generations, they just get better specs and OS updates.
Gears 5 for X1X (5/5) - Mortal Kombat 11 for X1X (5/5) - Doom 64 for N64 (emulator) (3/5) - Crackdown 3 for X1S/X1X (4/5) - Infinity Blade III - for iPad 4 (3/5) - Infinity Blade II - for iPad 4 (4/5) - Infinity Blade - for iPad 4 (4/5) - Wolfenstein: The Old Blood for X1 (3/5) - Assassin's Creed: Origins for X1 (3/5) - Uncharted: Lost Legacy for PS4 (4/5) - EA UFC 3 for X1 (4/5) - Doom for X1 (4/5) - Titanfall 2 for X1 (4/5) - Super Mario 3D World for Wii U (4/5) - South Park: The Stick of Truth for X1 BC (4/5) - Call of Duty: WWII for X1 (4/5) -Wolfenstein II for X1 - (4/5) - Dead or Alive: Dimensions for 3DS (4/5) - Marvel vs Capcom: Infinite for X1 (3/5) - Halo Wars 2 for X1/PC (4/5) - Halo Wars: DE for X1 (4/5) - Tekken 7 for X1 (4/5) - Injustice 2 for X1 (4/5) - Yakuza 5 for PS3 (3/5) - Battlefield 1 (Campaign) for X1 (3/5) - Assassin's Creed: Syndicate for X1 (4/5) - Call of Duty: Infinite Warfare for X1 (4/5) - Call of Duty: MW Remastered for X1 (4/5) - Donkey Kong Country Returns for 3DS (4/5) - Forza Horizon 3 for X1 (5/5)