This is generally unknown, of course. However it currently appears that the expansion of the universe is accelerating, i.e. it is expanding faster and faster.

Obviously it can't be ruled at that at some point this would stop and/or reverse. But there's no reason to think so, and if we're considering arbitrary future changes then we may as well consider that the universe might suddenly start heating up again in the future, or more mass will start appearing out of nowhere. Or god appears and hands out free decryption keys to everyone.