I'm assuming you talked to the potential client about a week ago? It's kind of hard to say with RFPs...it could be that they found someone and realized they couldn't feasibly get back to everyone who'd submitted interest. But with the holidays going full speed it's also likely they're just busy.
I think you can safely get in touch with your client sometime after
Christmas (if they said a week then give them an extra few days to get in touch on their own). But when you do email you might say something about hoping they had a great holiday and you're following up on the RFP, you're still interested in their project...and if they have any further questions for you...etc. etc. to kind of get the ball rolling.