According to a recent study by the Convention Industry Council, 85% of all conventions are held in venues that include lodging.
I'm not going all Heywood on you (because his "proof" is so suspect).
What I am saying is that stand alone convention centers without an attached or adjacent hotel seem to only work in major markets where people will be willing to walk, cab and shuttle. The future for second and third tier convention centers is clearly that of the John Q. Hammond model.
And, I'm so waiting to see who steps into his shoes.