Regarding what AAF said, officially their position as far as I can tell is that if an opportunity presents itself sometime in the future they might look at Tampa.
What I am speculating here are just my speculations based on informal chats with individuals, not with AAF, so it should be taken with an appropriate pinch of salt.
My speculation, based on some random conversations with people who shall remain unnamed is that once the Miami - Orlando thing is in place and running, doing a Jacksonville add-on is a trivial well constrained and understood problem with a relatively modest pricetag which involves almost no property acquisition issue. Everything that is needed is already owned by the Fortress Group (FG) in some way shape or form. It fits the FG model of building real estate developments and a railroad to connect them together. So most likely it is just a question of when, not if. In addition Jacksonville is already planning on it and setting aside access routes and such to the Transportation Center that they are building by the Convention Center, the old train station. They would really like both FEC and Amtrak to operate out of there.
Orlando - Tampa is an entirely different kettle of fish that is way outside the normal FG pattern. It involves others properties that have to be acquired and it presents relatively little opportunity for FG to build out huge real estate projects on its own property to justify for them the expenditure of putting a railroad together. So that one is a big "if" question first. Does this mean that no one will build Orlando to Tampa? Of course not. But it does mean that FG is likely to be much more circumspect about it. As Brian_tampa mentioned, one factor in favor of a Tampa project is the potential of a huge ridership, and that might indeed help answer the "if" question favorably even though FG has little property to develop in that part of Florida as far as I can tell. Certainly any significant windfall in the way of infrastructure development support from the private industry focused administration in Washington could help a lot there too.
BTW, did you know that the guys who were peddling the Maglev system (now defunct) for OIA to Convention Center had grand plans to then extend it to Tampa? Of course there was no funding for any of it beyond a dream and a prayer or two.
Again, no, no one from AAF said this or anything else that I have been babbling on out. It is my observation looking at past and present behavior patterns of the Flagler descendant operations which Fortress seems to be following. Their primary interest is in the Real Estate development and feeding business to them. So much so, that they are willing to sell off the FECR freight operations while retaining the underlying real estate property. My conjecture is that people who think the Brightline model can be replicated elsewhere and Fortress will do it, are in for a disappointment. Someone else might do it, but I don;t really see Fortress doing it in the near to medium term future. An interesting tidbit that many don;t realize, or forget, is that AAF and FEC Railroad are not even within the same subsidiary of the Fortress Group. FECR is a direct subsidiary of FG whereas AAF is a subsidiary of FEC Industries, which is a subsidiary of FG. The relationship between AAF and FECR is truly arms length, and recently there have been rumblings in the industry about FG trying to peddle FECR to short line operators. That also partly explains why they have kept AAF and FECR very seperate when dealing with regulatory matters too.