Highly unlikely for a couple of different reasons, the first is a dilution of the product like people have
The NFL likes to expand in twos and what would the second franchise location be after Los Angeles? There are three teams that split New York state, 4 3 teams that split California already, unless you are going to try to add a team in Texas which is unlikely
You have to deal with redefining areas, in terms of television for local broadcasts, and that is decided by the league, not the networks. If you place a team in San Antonio you cut into the Houston Texans territory, if you place a team in Oklahoma City you cut into the Dallas Cowboys territory, if you put a team in San Jose you cut into the 49ers territory, place a team in Portland you cut into the broadcast territory of the Seahawks. What team are you going to shaft in terms of exposure?
The franchise fee wouldn't be anything that important to the owners because of the additional splitting of shared revenues would be a long term negative play.
The most likely case would be for relocation of Jacksonville, San Diego, or Minnesota most likely to Los Angeles.
Las Vegas will never be a home to a team from a major professional league because of the sports books in the casinos and the state of Nevada isn't going to get rid of one of its biggest tax revenue streams in sports betting.