I look at Trump as a mentor for Cruz!!! Cruz could be ready in four years to take this mess over, after four years of Trump it will be back on track and easier for Cruz to step in!!! I DO NOT think Trump had ANY desire to stay more than four!!!!
That would be the ideal. However, first the NBC issue needs to be resolved. Until that is clarified, all else is mute. If Trump would want to serve for 8 years that would be agreeable, but, like you, it is felt he would prefer to go back to his business and continue his career from that vantage point. If he felt all which need a remedy had not been addressed, would he once again go thru the carnival of primary and election in order to complete his mission? He would be 4 years older and tired. At this point it is difficult to see how Trump and Cruz could ever be a duo but stranger things have happened.
Only loser quit. Does Trump want to be a loser?