It's number 1 I think. A connector between the current terminal and a proposed future one. Here are the overall plans. And here is the doc that most clearly shows the intended use of that structure.I've heard 2 different things on what that ramp was built/designed for.
1. A connecting service (either Bus or light Rail) with the MCO Southern Terminal complex which was postponed/canceled after the 2011 travel downturns. http://en.wikipedia.org/wiki/Orlando_International_Airport#New_terminal
2. the high Speed rail link station at the airport.
It's a built out for future rail access to the airport.