That is totally up to you. The current nightlies look very similar to how an eventual kicad 5 release will look like. But the documentation is still lacking (This will not change just because v5 is released. It will take a while till user build documentations catch up to v5.)
Another problem is that your personal library setup is not handled well on update. (The fp-lib-table will happily continue to point to the old official v4 lib. But the symbol and 3d libs are installed from version 5. Meaning without user intervention you end up with a set of libs that is out of sync.)
I would at least suggest to use the backport libraries as it will ease transferring the project over to version 5 (Assuming you use the official library. Otherwise this is not really necessary)