Honestly at this point I'd wait for the PS5, especially if the backwards compatibility rumors are true. We're supposedly going to get more info tonight with playstations state of play stream.
The data transfer should be ok. If in doubt, use cloud saves.
As for PS5, it could cost, like, $500-600 and may not have any worthwhile games in its first year. It's the same dealio every generation, if you didn't early adopt PS4, you won't early adopt PS5.