If you extrapolate the flight path after the change of direction (if the reports about that are correct) it continues on to Diego Garcia. Obviously, a US base would be an attractive target to muzzie terrorists.
However, I think India is more likely as a target, as a crash in the middle of Mumbai or a similar city would be more along the lines of the effect the terrorists would want.
I think it is very unlikely their plan was to fly it to a hidden airfield somewhere and use the plane later. Too much risk of detection before they could use the plane for a later mission.
Most likely the plane crashed into the Indian Ocean.
I should add that Hyderabad or Bangalore might be attractive targets for terrorists and easier to reach than Mumbai.
That 777 is going to more than likely make a surprise appearance in America. Remember Flight 92 that was going to take out the White House? That’s unfinished biz for the Muzzies. They could also take out NYC.
Time to put up a target list of cities and possible dates when it will show up.