Could someone please explain what will happen to the pool after the 5th block is found?
Sometime after that the 6th block will be found.
Ok, not very helpful but with some reading between the line of your statement. No reset, and the users who join now will get a share of blocks 5-9?
Don't read between the lines of my comment because I have no idea what you are talking about. I suspect that after this pool finds five blocks it will continue to find blocks and continue to run normally.
If you want to know how this pool works you need to read the top post and the pools web site.