1) Even if the "xbox one x", is forwards compatabile to play "Xbox 2" games... it probably wont be able to play Xbox 3 games, or Xbox 4 games.
2) Xbox 4 is along way away.... by then no one will have a xbox one x, playing online, the same games as the xbox 4.
Thats just silly imo.
People are really buying into this hook, line and sinker.
(instead of useing abit of critical thinking)
Xbox 4 was referring to the 4th generation Xbox, not 4 xbox generations from now.
Still... lets assume 2020 for xbox 2, and then it last another 8 years, before the xb3, and another 8 for xb4.
You expect someone in 2036+ to be useing a Xbox One X to play then modern day games?
Common, cut the crap.... your way overblowing this Forewards and backwards thingy.... at most its likely to be 1 gen it applies too.
By the time a Xbox 3 is out, you wont be able to play those games on a Xbox One X from today (imo), much less the Xbox 4.