Well, there's already been confirmed LBT 13, right? So that means there's at least going to be one more movie.
The series is good, yeah, but I woudln't want it to replace the series. There are some little stories that can't take up a whole movie, so that's where the series comes in. It should be used to display those events that can't make it into the movie. Sequels should be used to give us a larger story that can't be explained in 22 minutes, like what they should've done with Ali's reintroduction and such. Just so long as the movies and the series don't start contradicting each other (ie, refering to things that have happened in the series, but not having Chomper and Ruby in the movie), then I'm fine with both.