An online game can only be saved from cancellation and abandonment if it is peer to peer or runs on an open server architecture. Otherwise, the power to turn it off resides in the hands of one company, and they can do what they want with it. And if it is already running on an open architecture or community-controlled servers, then nobody can even threaten to shut it down in the first place, so it never needs to be saved in this sense at all.
As time goes on, however, such a project still runs the risk of being outpaced by updated hardware. What used to run on Windows 95 and Pentium chips now has to deal with Windows 8 and ARM chips. Interfaces that were designed for hardware keyboards and mice don't work so well with touch screens. The software may live on, and the core concept may never die, but unless it is maintained and updated, it won't continue to be usable. Keeping software alive and functional requires constant effort, and that effort might not be best spent on maintaining old versions instead of writing new software to do the same job, or writing something else entirely.
Mokalus of Borg
PS - This has been on my mind since City of Heroes shut down.
PPS - All the community effort to save it was in vain if the company wanted it gone.