I don't believe any of those games *removed* content upon releasing expansions. I haven't played them, so someone feel free to correct me if I'm wrong.

They haven't. Gear and items always get replaced by better gear in mmo type games, BUT you can still buy gear made from 10 years ago. WoW for example: -Has access to all previous instances, raids and dungeons. No lockouts. The que lets you pick from a list. If you want to play 10 year old content you can. They also have reworked all the old instances content to work with current que protocols. - Legacy vendors for gear no longer accessible from the current gear vendors. - all pvp battlegrounds are available. - expansions don't overwrite existing content and make it accessible. If the zone has a new quest line in it's area, they use a technique called phasing to not let you see it. While other people are playing the new content 5 feet from you. They figured this out when Cataclysm released. That's just a few examples of how WoW has not compromised your old purchases in any way. -