I agree, in season 6 you really got the sense that they weren't interested in doing a lot more with Elena's character because of obvious BTS reasons, but then in season 7 they kept the coffin at the forefront of a lot of the storylines, and that never made much sense to me when they were presumedly planning then to run for a few more seasons without Elena's presence.

It would only have made sense if they were planning to end the show with that season, and already setting up for a finale with Elena waking up, instead it really stagnated the show when they had a good opportunity to shake things up with Stefan and Damon. They could have made much more of that slightly post-apocalyptic feel in the season 6 cliffhanger for one, instead of ultimately only going a few years into the future