I don't think the population between 2008 and now has changed too dramatically. I'm sure it has gone down some, but that goes for all games really as far as paying subscribers. You'll probably find quite a few upgrades that were brought in with the Legacy of the Xan expansion, but nothing that's out of reach if you have an org that is willing to raid with you.
I'm assuming since you are wanting to bring back your 220 doc that you are planning to go paid again, so it would probably be in your best interest to grab the LoX expansion. I'd say there's not a ton of PvP anymore, though certain battle station ranges (mostly towards the high end) are still very active because there's a daily mission associated with them. Tower battles aren't very frequent anymore, and the new PvP area never really caught on.
It does look like they're putting in a nice semi-pvp instance for Halloween though.
The addition of daily missions makes leveling a very different experience because even if you just have a 30 minute or 1 hour time window, you can do a daily and get a level of regular xp until the later levels, and alien levels too. Makes it feel like you're accomplishing something instead of hanging out on LFT for 6 hours trying to get an inf team or something
I think it's really a matter of finding the right org if/when you come back. If the org doesn't really do raiding, you'll have to sit on LFT or join a raid bot and hope you get lucky enough to get the loot.
All in all, the game is still very enjoyable. Playing a new character can be a lot of fun when you are able to start gaining normal perks, alien perks, and research perks from the get go. It really changes how you play the game.