Apparently Plot 6, the obvious place for a bus/rail interchange that could share the station's new passenger facilities, is not in Network Rail's plans. They have spoken, though, of an 'interchange' more like that in Old Market. A couple of new bus stops, in fact!
I think the LEP» (Local Enterprise Partnership - about), who are leading the 'partnership' of different public agencies, including Network Rail, that's building a 'strategic vision' for the whole Temple Quarter Enterprise Zone, don't have a proper transport hub on their agenda either. The nearest we can get to their thinking is a 'fly-through' concept video complete with lots of artists impressions of waterside piazzas and coffee shops. It's at https://www.youtube.com/watch?v=q3hAC3NyIvk . Quite entertaining as an example of its craft, but probably created more as a marketing tool than to inform.