@SonicTMP Except progression is entirely separate in both games and NGS won't even launch with all existing PSO2 classes either. It's a new game as well as a reboot that we will just happen to be able to share things from the existing game with. It's more like the Mass Effect series at best where you can think of it as a partial save import.
Seeing as they've said all your weapons will transfer over but won't be usable until you level up means that most if not all the classes will be in the expansion. Maybe the scion classes won't be as they are just hybrids but the main 9 will all come over. Everything shown so far functions exactlly like any other mmorpg expansion does. New xpac levels, new xpac mechaincs, new xpac currency, new xpac items weapons and gear while still letting you use the old stuff even if it works slightly differently. And you can go back to do the old content whever you want with your same character. That's how an xpac works.