Intrestingly enough Denver's Union Station was pretty isolated up until about 8 years ago.....like Jacksonville, the station is at the far edge of the CBD.
The difference is that Denver built a new baseball stadium and riverfront park in the area which, in turn, led to new residential and nightlife development....now the gap between the station and the rest of downtown is all but closed.
Can this happen here? Of course! But, as has been noted here many times, investment in dwntown Jax. has been scattered around...if we want a transit neighborhood, then we need to focus new devlopment to the area around the proposed transportation center.