Patents are not intended to encourage innovation. Innovation happens all the time without patents. Patents are intended to
abolish trade secrets! The bargain society offers with patents is
tell us how you did it, because we know you're going to do it anyway. But if you tell us how, we promise to not compete with you for a short while.
If the trademark on Mickey Mouse were used forever, this doesn't mean we can't pass Steamboat Willie around. If its copyright expires, we can copy it, we can reproduce it, we can exhibit it, we can remix it; we just can't confuse the public into thinking we're Disney while we're doing any of this. If Disney thought it could prevent people from copying Steamboat Willie without copyrights, it wouldn't be lobbying for infinite copyright on it. The best Disney could do is make us state, in no ambiguous terms, "Mickey Mouse is a trademark of the Walt Disney Company" somewhere very prominent while we do whatever we want with Mickey.
A trademark doesn't mean that the trademarked thing is Lord Voldemort. Otherwise, every time we said "Microsoft" or "Apple" we'd be infringing. It just means that we might have trouble calling our OS "Hackintosh" or "Lindows", and even that's debatable in court (Microsoft was about to lose the Lindows case).