Straight from the developers mouth:
No Mac apps, no gimmicks. Procreate is actually drawing at high definition resolution using OpenGL graphics acceleration. Just export to photos, and check out the 1920x1408px size!
Coming soon as a free update.
Savage have even provided a couple of HD painting examples. Check them out for yourself here and here. We've printed out an A3 sized full resolution poster of the painting seen in the video above, it looks gorgeous! Savage are really pushing back the boundaries, this new canvas size will make a huge difference to the final quality of printed paintings.