I don't think anyone at Paramount/CBS have said it isn't going to happen. It will probably boil down to how much it costs vs. how much they think they can recoup by selling both shows to tv again, and Blu Ray sales. The 50th anniversary will create demand for product besides a new feature film.
DS9 and Voyager used more CGI than TNG ever did, but I've heard elsewhere the files were saved, and could be re-rendered in HD.