I say 5k
In my opinion probabl yback to around $4k or so.
Right now the price is going absolutely bananas. I don't think that this is going to continue forever because that has never happened with any asset class and it is just not sustainable to see this sort of huge profits every single day.
It could even before the fork, if people start panicking.
I'm going to go with in between your estimates, so a slow retrace back towards 4,500 after Segwit2x fork, settling down for a fresh attempt to break $5000 after Christmas. It's incredibly difficult to predict anything with Bitcoin now. One one hand you've got big players happy to take profit every ATH, confident that even a day's dip will give them opportunities for re buys at 5-10% profits easily. On the other you've got a non-stop influx of new people, many of whom are big bankers and middle-class suits with deep pockets, so buying demand will keep raising prices.
Then you've got our highly contentious Segwit2x fork, which I suspect will be a lot bigger, with weightier reactions than we experienced with BCH ad BCG. Efforts from substantial camps to force customers to recognise the forkalt as actual Bitcoin might work, too, you never know.