I highly doubt that any park would be willing to build any coaster with a gap, mostly for insurance and safety reasons. Even if the technology is there, it just seems like a very abstract concept for a coaster.
Personally I think it would be very cool if the illusion of jumping the track were executed well, which is very possible:
http://www.cantileveredcoaster.com/AbouttheCRC.html
I would love to see one of these built!
Here's the site's homepage:
http://www.cantileveredcoaster.com/index.html