Short answer: no.
Longer answer: if you have a recorded shot of your weather reporter on green, and a recording of whatever the map has to show, that also has the same audio as the weather person, FCPX can automatically synch those tracks up by their audio, You drop the chromakey effect plug-in onto the green screen shot, bam, that’s done, more or less (can need some minor tweaking). Then as you play back in real time, you can hit the number keys like a live video switcher to cut from the composite to just the map, as if they were cameras on a switcher. But no, it’s not a live switcher.
There are free and shareware software-based switchers out there.