Limits on prop bets like this are pitifully small usually no more than a couple hundred bucks. Vegas is not sweating this action whatsoever. It's just a fun prop for people to throw a couple bucks down.
To answer your question, generally, yes Vegas will try to get equal action especially on heavily bet sports like the Super Bowl, NCAA Final Four, etc. However, they 'take stands' all the time where they are comfortable taking 70% percent of the money on one side knowing that statically they have the right side and are willing to take the risk.