Oh yeah it definitely makes more sense for the plot to keep the cure as an issue for Elena and Damon, but in character terms you'd think that Bonnie's Mom would be the one to get the cure after Bonnie found it. Although, then again, it is very Bonnie to always put Elena first in her life before thinking of herself :/

And I'm hoping that they're going to explain more on how those particular vampires managed to stay witches, it doesn't make a lot of sense otherwise after the emphasis that the show gave that with Abbie's plot.