I actually don't think it would be that bad. Learning T9 wasn't so hard. And I believe that the muscle memory for typing and swyping is totally different, at least based on my anecdotal evidence:

I've used Dvorak on all my computers for about 10 years, but my phones are still QWERTY. I've tried switching my phone to Dvorak, but found that the typos were much worse (because dvorak clusters all the most used letters on home row, which is close to the "worst" swype layout in the article).

For the times I tried Dvorak on the phone, retraining myself was indeed cumbersome, but I don't think it was too bad. I thought that it would be easier, since I had Dvorak in my brain, but the muscle memory for hitting a key with a certain finger moving a certain direction is totally different from swiping or taping a certain location on the screen.