Upgrade path from 4 Pro?

I have a 4 Pro 4x2, is there any path to upgrade it to 5?

I believe you mean Shapeoko Pro?

XL size?

As noted in the SO5 Pro announcement:

https://carbide3d.com/blog/introducing-shapeoko-5-pro/

Can a previous Shapeoko be upgraded to the 5 Pro? Unfortunately, they cannot. The Shapeoko 5 Pro is a completely new machine and I don’t think there’s a single shared component between the 5 and prior machines.

If you mean a Shapeoko 5 Pro 4x2, then the answer is still no — all the Hybrid T-tracks would need to be replaced, as well as both Y-axis rails, plus the wiring harness — the only part left would be the gantry — all 3 sizes were available at launch, so the expectation is folks will select the size which they want.