I remember where I heard it. It was on that Behind the Scenes program E! used to way back when they first started. I just found the video (being a packrat is insane) and Berman says one of the reasons that TNG ended was they wanted to make it into a movie property and they were worried that being able to watch it on television would hurt ticket sales.
A, that was just one of the considerations that went into the decision. And B, it wasn't just Berman's decision, it was the decision of the studio executives he worked for. I get sick of people online assuming that every single thing they don't like about Star Trek
is the fault of either Berman or Braga or both rather than actually trying to get their facts straight.