You can play old games for many years yes. But after a while it gets boring anyway.
Some of the 10-20 year old RTS games got released as HD-editions recently. But they are just the same old games. What is really needed are new games with new content. Not just lame cheap re-releases named "HD". The world needs new Triple-A RTS games, that are not clones of Star Craft 2. Star Craft 1, Age of Empires and Command and Conquer series were better games in many respect and this is what is missing today - non-causul non-F2P new RTS games with realistic scenarios like in C&C Generals and Age of Empires or Empire Earth series.
Aoe2 has got a couple of expansions that added more factions, however from my perspective I don't really look for more content in updates as much as better features... Spectating a game in aoe2 is a joke and watching the casters struggle with disconnects and having to synchronize replays is kinda sad.
