Nothing will happen.  This is not a contentious HF but a network upgrade the result of which is that only those running the new software will be on the network.  The coins themselves don't change in anyway.  Monero forks every 6 months so it has gone through this process several times already without any problems.  Hard forks are done because Monero is still in very active development.  Please note that it is an entirely different code base than btc.  Most alts are just btc clones.  Monero is a leader.