B5 died a happy and proper death, which is more than you can say for half the TV series out there. They ended the story nicely, everything was all wrapped up. And they even got a cool spin-off mini-series and movie out of it, to give the fans something to chew on. It was as graceful an exit as Hollywood has ever afforded a series, so I say let it be.
I'm against any moves to milk the franchise unless they could do a full new series, with proper budgets and a commitment from a major network, so that they would be able to create new show with new characters and story instead of dressing up all the B5 guys in their old costumes and trying to hide the passage of the years.