PEQ's release of Velious doesn't have anything to do with network encryption. The team is taking it slow and going one expansion at a time with their releases.
You are perfectly free to zone to other expansions, as I believe all zones up to GoD (maybe OoW) are there and available to zone into. Just don't expect to find any mobs in them
Note that by default, only GM's can zone into zones past Velious, though this is a database entry and can be altered at the server op's discretion.