It will impact the other profiles on your current Xbox, but not yours. Your Xbox Live profile is designed to follow you to one other Xbox, so that is why it works for you to use yours on your current one while he uses his profile on his Xbox. His Xbox HAS to be the home Xbox though, otherwise he can’t use his profile for Live and would have to log into your account resulting in it logging your profile out on your current Xbox. So, his Xbox will be your home Xbox giving him Live, and your Xbox will be your “guest” Xbox but you can still use Live when you use your profile because of how it is designed.
I almost forgot, setup his profile on the current one and make your current one HIS home Xbox as well. So your profiles will be on both. He will take the Xbox that is your home Xbox, and you will keep the current one set as his home Xbox.