PoS has been proven to be quite secure by now. The only reason Bitcoin doesn't change, is because miners would not agree since it would make their hundred of millions of dollars worth of equipment obsolete.
Doesn't PoS just make the rich richer?
Everybody gets the same amount of interest on their coins, so it's false to say that only the rich get richer.
Plus, the same criticism could be made about Bitcoin because of deflation.