At the end of the game, a free roam mode in all playable areas from all the games would be absolutely great. This would include Dobuita, of course, and since someone would actually have to design and implement Dobuita for the new game, they are hardly likely to look at the cinema under renovation and say, "Well, we'll leave that as it is." Whether it would have "playable" features, like the cutscenes and extras from Shenmue I Disk 4 would be a different matter.
According to a preview of Shenmue the cinema was supposed to be gradually completed as you progressed through the game, but apparently that did not happen in the finished product.
Story-wise, I'm firmly convinced that the playable part of the saga will end in China, but that Ryo (assuming he's still alive) will return to Yokosuka and to the Dojo in a long ending cutscene in which he is re-united with Fuku-san (much matured due to having to run the dojo on his own) and Ine-san, and of course to introduce them to his bride Shenhua!