tbh, DHS doesn't have much expansion space. It's blocked in by main roads, an access road to the park, backstage stuff and wetlands (which technically could be used, but it would cost a lot just to prep the land).
Right now, the Backlot Tour area and where Lights, Motors, Actions is IS the expansion space for DHS. For all intents and purposes, if they do a proper replacement, it WILL be an expansion as far as the public is concerned because more people will actually care about what is there.