Not quite. Going from pure 2d, to 2.5d is not the same.
With 2d, you get (for example) 40000*40000.
To double (in the same chip area) - you need to go to 60000*60000, or 40000*40000*2.
You can do this several times.
You may reach 40000*40000*8 - you are not going to reach close to 40000, without the chip fabrication costs getting completely out of control.