Does anyone know the dimensions of the XL2 relative to the Xl1s, I was wondering if it will fit into my existing case? (with and without the 20x lens)

Depends on the case. It won't go into the reflective aluminum "steal-me" Canon cases but it will fit in the Kata, Petrol and PortaBrace XL1 soft shells.

The dimensions are:

(W x H x D): 8.9 in. x 8.7 in. x 19.5 in. (225mm x 220mm x 496mm)

Weight, body only: 5.3 lbs (2.4 kg)
Weight, equipped: 7.8 lbs (3.5 kg)

Hope this helps,