The rule is, you can't be ELECTED more than twice (which is incoherent as an Amendment, because Presidential elections do not exist in the Constitution).
But I digress.
There are ways to become President other than being elected, and all of them are available to Obama.
“There are ways to become President other than being elected”
You could be vice president, then the president dies or whatever, then you’d become president. What are the other ways.