He will announce and run, because he is willing to go against Obama with his billions.
Why?
Because Obama will do whatever its takes to flood the election with money, if he had $2 billion in donations last election he will spend 10 times as much the next time, money means nothing to him.
Any other candidate just simply cannot compete with a limit election budget, money buys the votes.
Obama has created an oppositional power vacuum that only a guy with Trump's brass balls and money can fill. Trump knows this and is perfectly willing to take his place in history.
Except for Governor Sarah Palin. I will personally raise $2 million dollars for her campaign war-chest. There are tens of millions of people like me out there.