Does anyone know if network need re-sync after upgrade to rc5, or can I just copy over?
You need to resync
No you don't need to rescync.
I just put my database folder and my wallet data and it was working with no problem. I always check first like this way.
There were some complaints on Discord that it doesn't work with the old database...so just to be on the safe side I recommend you to delete old databse and do a full resync.