In general, a tag should not refer to two separate games, especially if those games are completely unrelated. So, an edit that makes a single tag refer to two different games is incorrect, and if such an edit is made, it should be rolled back like any other incorrect edit.
In this particular case, we have an unusual situation where a new game has a stronger claim to an existing tag than the current game does. In this case, we have a few reasonable options:
- Tag the new game with evolution-2014, or something similar. This would mean that the tag name is an artifact of the order in which the tags are created, which is suboptimal but workable.
- Tag the new game with evolution-2014, then have the moderators rename evolution -> evolution-origin and evolution-2014 -> evolution. This would make the tags more closely match the game titles, but it's more of a pain to implement.
- Tag the new game with evolution and retag questions about the old game to evolution-origin, then update the tag wikis to match. This has the downside of having the tag wikis be temporarily incorrect.