Texas has no statewide ban on billboards. Only Hawaii, Vermont, Alaska and Maine ban billboards statewide. There is little risk of the others following suit, as they would have 40 years ago if they were going to do it. Most states see billboards as a necessary tool for motorists to get information on food, hotels, and other options. Even the original Highway Beautification Act sought not to outlaw billboards but to simply control them. They could have banned them nationally just as easily, but they did not. The markets you are talking about (Dallas, etc.) are so picked over that there's no decent locations left anyway, so a ban would not even matter. To find good billboard spots today, you have to look outside the major cities. That's been the case since the 1980s.
The LED issue is that cities are trying to limit them by requiring removal of other signs. They are basically trading billboard companies something they want (LED) for what the cities want (fewer billboards). You can't blame them, it's not a bad barter on their part.
Nowhere that I'm aware of bans repair to billboards unless it exceeds 60% or so of original cost -- essentially total destruction from a windstorm. That's been the law since the 1970s. I've never seen a sign come down as a result, except in a tornado. Most operators work around the issue and do renovations a bit at a time.