You won't be the first person to have sex and/or sleep on the floor if the bed gets too small.
Is he coming to stay at your place, whether you have sex or not? If you don't have sex, where are you expecting him to sleep?
If the only choice is to share your bed, then that does raise his expectation that you will ,indeed, have sex. If you do want to "see where things go" without commiting, perhaps you should organise him some alternative sleeping arrangements (couch etc.) - these don't stop you having sex, but it means things can go either way - and he has to work a little harder to get in your pants!