I have amassed a large IP blacklist myself, but i would certainly not consider deleting any of them. They were added for a reason, primarily because they were a repeat offender. Unless some of the blacklisted IPs are causing some sort of remote access issue, I'd leave them in place.
If you delete them, you'll just have to start over again.
If these are local IPs, and a result of the upgrade, then consider white-listing the local LAN.