Microsoft has already made it clear that the Xbox One will not be able to play Xbox 360 games. This can be a slight issue for people making the switch, because depending on how many Xbox 360 games they have, they will have to sell them along with the console.
They could keep the Xbox 360 console, and play the games, but in 8 years time when Microsoft shut down the Xbox 360 server, the games will practically be only useful as a coaster. Making the change from 360 to One is simple in our eyes, sell the 360 and all of its games while you can, getting a good enough price for the lot, and start again with the Xbox One.
Annoyingly people will have to buy the same games again for the Xbox One, and it’s certainly going to be a costly process making the move.