Anytime a receiver is going to the ground he must maintain possession and control after he hits the ground. Simply breaking the plane of the goal line while going to the ground does not mean you have a TD. You must maintain control after hitting the ground. This is why you have replay because onfield officials can make mistakes.
This is true if you rule (in this play) that the whole action is a receiver catching the ball and going to the ground. Based on this single angle I'd rule that first you have the receiver catching the ball and completing the catch without going to the ground in the process, and then you have the
runner lunging for the goal line and going to the ground.
Or do you claim that no matter how much time elapses between the catch and the loss of control that it is always an incomplete catch? Catch made at A-5 and control lost while going to the ground at B-1 after a 94 yard run?