I think that it could in time. The key is that the poll is about the city limits in terms of population. Given Tampa's land area and recent propensity to annex suburban land and develop it, I think that it is inevitable that Tampa will become a "bigger" city than Miami.
And it's not like Miami is the only city in Florida experiencing inward growth these days. After today's big redevelopment proposal for some public housing in DT Tampa, there are now ~6500 units proposed to be built in just the DT area over the next few years. And this says nothing of the significant housing growth at both the University of Tampa as well as USF (the schools combined plan about 4,000 units within 10 years), which could bring in several thousand more residents within the city's juridiction...
I sure don't think it will happen any time soon, if ever... But it is a real possibility and nobody should really be all that surprised if it does happen 30-40 years from now.
"We see things not as they are, but as we are." - John Milton