There's finally a rendering of the proposed convention center at the jail site, from the DIA:
However, as you can see, the jail itself is still visible behind the convention center, only the police building appears to have been replaced. Which either means that this rendering was lazy and they didn't appropriately account for the physical space of the convention center, or it's much smaller than previously suggested.
Which actually leads me to think: I think we've historically assumed that the police building and the jail would stay together or be replaced at the same time, but that's not actually obligated, is it? Could we just build a new police building (one spot that comes to mind is the block bounded by Broad, Adams, Clay, and Houston streets next to the County Courthouse), rehab the jail, and use it for another decade or two with provisions to eventually hold an expansion of the convention center?