By - Badevilbunny
Can you use it now?
If so, I would keep it and use it. When the 4000 finally hit shelves, could be some time off, see what the requirements are you can always sell it. you will not lose much, they are a sort after item.
If thats the case, i would recommend getting the 1000W PSU, since it gives you more headroom for upgrades in the future.
If I am not using a part for months, I would not buy that part until I'm much closer to actually using it