In my experience no, I've dropped lots of things and left many things on the ground and they're all still there. However, there's most likely a limit eventually. It could be in the 10,000s, meaning you'd have to drop 10,000s of other items before it removes the oldest one, but it will almost certainly work that way.
If you're worried about leaving something for a while and then coming back to get it, that shouldn't be a problem. It's just that unless the save file can grow to an infinite size, there's going to be a limit, even if it's so high it doesn't realistically matter.
I really wish we could get some confirmation on that. I found a chest that I can actually place in game and use as a stash box, but I'd hate to load it up with stuff and have it vanish 80 hours in or something.
