Would be interested in this as well. Any updates?
Yeah it's been a long time with zero updates. I've read a dev say it's not possible, but that seems crazy to me. The saves are clearly compatible. I've transferred them between devices myself with no problem. Other games use steam cloud and it works between OSX and Windows just fine. Surely it's possible.
Uninstalled Pillars from my macbook yesterday actually, because I kind of gave up on this update. Hopefully it'll actually happen sometime though. Until then, I guess I'm stuck playing it at home on my desktop.