Online? I would assume they are not changing their Xbox live set up, however, being that the Xbox one games are not backwards compatible you may not be able to play with people using the 360 because they might set up separate servers. The official Xbox website might have information on this or ask someone who works in a gaming store.
The games arent reverse Compatible so you will have to buy the game again to play with them online. You will have to play on a 360 to play games with others most likely. No next gen consoles will be able to play previous gen or current gen games unless im assuming you get them off of the online stores