He isn’t going to run against Cruz but he can self finance indefinitely which is a fact that all candidates need to start strategizing for.
At some point in his campaign, especially if he has momentum, I'd like to Trump announce something like this: "I have earned enough money to finance my presidential campaign, but I am going to ask Americans to help me out in another way. Please send $1 - and $1 only - to my campaign. Think of it as "early voting". That will send a message to the appeasers on both sides of the aisle - or it will send a message to me (grin)."
I think he'd get so many $1 bills, the others would be jumping out of windows.