It is my understanding that an almost identical structure was unearthed in Caesarea. It was an octogon, like the dome of the rock, and turned out to be a Byzantine Church. Also the Dome is unlike any other so-called Muslim design. My guess is that is exactly what their Holy Site is, a converted Christian church.
I believe in Revalation that John was told, when measuring for the Temple, to leave the courtyard to the Gentiles meaning don't measure it. There is a teaching that says that a newly constructed Jewish Temple will actually sit next to the Dome. I guess it's possible as the result of a "peace" settlement.
I don't know what God will do, but I have total confidence He has a plan for it all.
Given the history of the Temple ground--the land there---it is clear, very clear, that God has assigned significance to it.
He will take care of it. But the world should better prepare itself--it may not be pretty.