Yes, but it isn't very likely. If you'd like to mod your gamertag and want to minimize the chance of getting caught you should do it without symbols/colors/xbox controller buttons or any other sorts of effects that will immediately give you away if a mod is present in your game.

dude ive modded my gt like 6 times today and nothing happend but you still could probably get banned for a couple days but you just gotta take that risk

Yes there is a chance of ban.