Well, CSX certainly knows how to bargain. The only way to put local commuter rail in Orlando was for FL to buy 61 miles of track AND create a bottleneck that might prevent SunRail from ever being extended to Tampa. I can see Tampa, in time, opening a commuter rail line to Lakeland, just west of where the S line comes in from the north, in that case, it would only be a matter of time before people call for the gap in service to be closed. But that's so far in the future it's almost not worth discussion today.
The state may only be buying 61 miles of railroad. But in effect are they getting almost 200 miles from Auburndale to Jacksonville? CSX will still demand additional payment for service extensions. Nonetheless, this arrangement will facilitate incremental commuter extensions north and south (as far as Auburndale anyway) as the need arises. It may also make it easier to implement a 401b train between Miami and Jacksonville via Orlando to supplement the Silver Star. I know, I'm not holding my breath. :p
Now this question may be better suited for the CSX section, but because it's closely related to the creation of SunRail, I'll put it here anyway. CSX should probably go ahead and double track the section between Auburndale and Lakeland now. I just don't think the south wye at Auburndale can fit a second track. This is the leg heavy freight traffic to the Winter Haven yard would use but it is squeezed in by industrial buildings which, incidentally, are also CSX customers.