I think I read that TBBT was picked up for another two seasons, which I am very happy about. I think the show is still doing a good job of staying fresh and entertaining, but I think the end is starting to come into sight. The series finale will probably involve Penny and Leonard getting married, and/or the dispersal of the group. I don't think that can hold on for more than another two seasons, though let's not forget nine total seasons is extremely respectable for today's TV shows.
While I have no complaints, it seems as though most of the humor from the shows now comes strictly from matters involving Sheldon. It works because Sheldon is funny, but the jokes are often at the expense of his characters development. I.e., he was suppose to evolve in many different ways (like his relationship with Amy, having more human feelings). There's not much left for Howard and Bernadette, Raj's girl situation is fairly boring, and there's nothing left for Leonard and Penny either except to get married. I doubt after their 7 season relationship roller coaster it would end without them together.
The question is what else is there to fill the episodes? Sheldon needs to find a new area of theoretical physics to focus on but I doubt that will be much interest. There can't be any more long research trips or major relationship shockers lying in wait. Though if Sheldon does ever sleep with Amy, consider the shark not only jumped, but caught, killed and weighed; so let's hope the writers don't get that lazy. Continued guest stars always help individual episodes as well the general story line become more interesting. Aside from this limited amount, I hope the writers have some good plans for the next couple seasons before it ends with a big bang! The fact that it will premier this fall at it's new air time on Monday nights at least shows they have faith in it.