Broadcast TV going completely away shortly? What makes you think that?
I can think of several reasons to have an antenna:
1) Many campgrounds, and virtually all boondocking locations have no cable TV available.
2) Satellite reception requires either a teadious set up procedure or a big$ tracking type system. On top of that you have monthly service fees, and possibly monthly equipment charges.
3) Over the air digital broadcasts still provide the best picture with the least compression of the HD signals. Better than cable, better that satellite services
4) Depending on the type of antenna and proximity to the broadcast location, you can watch the networks while rolling, something you can't do with cable.
5) Feeding the signal to a second TV in the bedroom is simple with an antenna. With a satellite system it becomes more complex. Either both TVs must watch the same show, or a second receiver (at extra cost) is required. Even with the second receiver, you may run into issues if two shows are on different satellites. Possible need for multiple LNBFs, etc.
6) Satellite reception requires an unobstructured light-of-sight to the bird. One misplaced tree branch at your assigned campsite could mean no satellite service during your stay.
7) Even if you do have cable or sat, having an antenna provides redundancy. Redundant systems are good.
Buy the antenna and the rest is free.