To be fair, Trump said “probably” he would run as an Indy but would seek the Republican nomination. Trump says he is in it to win.
Trump is looking at all of the angles. Trump needs to decide if he wants the job and if he can win. If both happen, we'll enter the race as a brand rather than a Republican.
For his planning, the first option is Republican which is out of his control. The second option is Independent which is in his control.
I think he could win as 3rd party. He might entice more Democrats and Independents.
If the Republicans promote a weak candidate, I'd seriously consider a 3rd party Trump because I believe he could win and he'd be a better choice that dumb or dumber.
Interesting times...
If he goes indie, he's not in it to win, unless handing the election to Obama is considered a "win."