Comparing the specs of the Carry to those of the P229, I'm seeing less of a need to continue with a P229. Time will tell.
A few other people have mentioned this also. I think they have a point. Compact versions of full-size pistols (with a Browning tilting-barrel type action) need to account for different locking/unlocking timing. In the old West German days, this was done with a different barrel lug, a different locking insert position/geometry, and a different recoil spring (the P225, P228, and P229 also had shorter ejection ports anyway because of the lack of longer cartridges like .45 ACP and .38 Super).
If you look at the disassembled pictures of the new P226-X and P226-XCARRY pistols, you’ll see that the XCARRY suspiciously has a Glock-style recoil spring assembly, while the rest of the pistol is all standard P226 hardware and geometry (instead of P229-1 like most of us would have expected it to).
But the P229-1 hardware is completely superfluous these days because SIG has abandoned 40/357 entirely. The old Legacy (P228/P229-9mm) hardware would make more sense, but it would still be more complicated for manufacturing than the new XCARRY hardware. The P226 has maintained the same internal parts since its creation, and it has remained the most relevant/popular model of the classic P-Series, so it makes sense to design a new series of “modular” guns around it. The XCARRY only needs a shorter grip (easily done) to completely replace the current P229-1 entirely.