I had one of these vent cap units above the co-pilot seat on our Georgetown and when you removed the cap, inside there was a raw ended piece of coax and a brown wire.....probably 12 volt. I was told this was factory installed as a prewire for rooftop satellite if you chose.
The cap unit looked like this......
Ken and Terry
2018 Sunseeker 2430S-CD
and if we ever need it, can be pushed by our 2017 GMC Terrain toad (4 wheels down)
Former Georgetown 330TS owner for 10 years with more mods than I can count.