Specially if you are considering leaving it as storage only, I'd say it's totally worth it sticking to CORE.
It's stable, tried and tested. And it works. Even if fancy new features like RAIDZ Expansion won't make it to the GUI, it'll probably work just fine from CLI.
I have a CORE box as my NAS / Home Server with many Jails running my stuff in it and I don't plan to switch from that anytime soon. Maybe if my services stop supporting FreeBSD, then I'd start by migrating them to Docker containers running in a Linux VM, and when all of them are migrated, then I'd consider going the SCALE route.