I would have a difficult time putting an estimated height on that site. One of the issues I see is that a chosen site has to be large enough to accommodate enough convention space, and what type of space requirements the county would have. Would they simply want smaller spaces similar to convention space in other hotels, or are they going to want more exhibition space with large footprints and tall ceilings.
If the desire is to add more exhibition space then the a site like the Royal Wood would have to be the prime candidate. (IMO it is the best location either way, no matter the space requirements) Placing the hotel on the Royal Wood site with a large foot print could easily limit the height, as the developer may choose to build more of an L shaped midrise design, as opposed to a tall slender tower.
If the desire is to simply have more meeting space, similar to other hotels convention space then they could easily pick a smaller site, such as The Shilo, or the Arrow Press Square sites. This would obviously require a much taller structure to get to the 1000+ rooms.
From what I recall reading though, the county is looking for more exhibition space, that will require a substantial footprint, thus making the Royal Wood site the best location choice. That is my long answer, here is my short answer
It all depends on how the developer/owner of the hotel wants to impact the city. Do they want to simply provide a CC hotel with enough rooms or do they want to do that as well as be a fixture in the skyline? Because the site could easily accommodate either option.
This is the exact reason I would love for a W hotel to be the CC hotel, because they don't do short, stubby and ugly. Heaven help us all if our cc hotel looks anything like the Phoenix hotel, I'd rather we not have one then have that one.