I haven' t watched the show in years either. To your question, I think it's a yes and no. Yes because she is one of the last major characters left; though I think Daryl and Carol are still on the show, and I've read that Maggie is open to coming back. With her gone, it takes a major draw away from the show. So I think it might keep going for a season or two after Michonne, but with Fear of the Walking Dead still running and a new show in the offing the writing is on the wall for the original series; Robert Kirkman ending the comic also feels like a sign to me that things are coming to an end for the original show. The x-factor will be the Rick Grimes movie (s) AMC is planning. Maybe those will inject new life into the original series, or they might just take more people away from them, if they care more about Rick than the other original characters.
