While not much, Jax has a few projects. I've been meaning to do something like this at MetroJacksonville.com but I haven't had the time to get around to it. Anyway, here are some proposed projects in and around downtown Jacksonville.
Laura Trio (Courtyard by Marriott)
Beacon Riverside
East San Marco
Madison Landing Apartments
SeaGlass (personally, I think this one is pie-in-the-sky)
Jacksonville Landing redevelopment
Barnett Building