No. I think the writers will pair up the couple with the most support. There would be no point ending the show with Stelena if the majority of the audience hate them.
Example: In the Gossip Girl books its all about Nate/Blair. But on the show Nate/Blair werent as successful fanwise as Chuck/Blair. It's now almost certain that Chuck/Blair will be endgame.
Yes. The show can be totally different sometimes but I think the ending will be the same. Because, IMO, both are Vampire Diaries, don't matter how different they might be.
I don't think so. I think it will change things when we know who Elena ends up with in the books, but in the end the show is completely different to the books. Also, as someone has already said, it can all go down to audience response. If everyone HATED Stelena, would we be able to guarentee they will be end game? The answer is no. However, I also believe that whether a couple is popular or not, the writers will write whatever they want so it will always go down to the writers having the most power.
So anyway to end, whether SE/DE/DB or whatever pairing is the end game in the books, I think the books will have about 20/30% influence on end game so I wouldn't think about it too much.;)
