Their fan base is ok, they're averaging over 21,000 a game but there always has been a grudge between Tampa and St Petersburg even before the team was awarded to this area. (Long story explained in another thread here)
However, investors are currently in place with plans to build a new stadium in Tampa and if all that happens, attendance with rise dramatically. The money and population is in Tampa, St Petersburg is mostly retired fixed income.
Personally I think it will happen based on investors wanting to buy into a winner but it will be several years off before they can get it done.