In March, on the 20th anniversary, Daybreak Games(new name for SOE) released 2 new Time Locked Progression servers. Have to be an All-Access Member, $15/month, which also gives you access to other Daybreak games.
Selo, which is a fast progression server, started with Luclin, and every month opened a new expansion until it catches up to Live servers.
Mangler, started with Classic Everquest, and released a new expansion every 12 weeks. It's currently on Scars of Velious.
I started playing on Mangler in March at the start, having a blast without totally committing all my time on it. It's not totally like Classic, it does have some of the more recent benefits, no corpse runs, maps, quicker experience. Some of the players on the server left when WoW started WoW Classic, but there is still a decent sized player base.
Luclin releases on 11/20, also, it's been running with Luclin models since release, but if wanted, the old models can be run. not sure if allowed after Luclin.