Is there a continuity plan to end The Clone Wars Series and tie it up to the movies?
As I imagine there are many unanswerable questions related to the star wars universe from the tv series.
Or is George Lucas just milking it as long as he can?
There are no definite statements about how the current series will end, as (supervising director) Dave Filoni has mentioned how the story is constantly in flux and an ongoing writing process.
That said, they will indeed have to wrap up Ahsoka's arc (and there are many theories about this), but considering this takes place in the period between the second two prequel films, it would make sense for the series to wrap up on the eve of the space war over Coruscant (which was wonderfully dove-tailed into Genndy Tartakovsky's animated take on the saga).