There's pretty good evidence to suggest it will be Iroas (R/W), Kruphix (G/U), Xenagos (R/G), Phenax (B/U) and Athreos (W/B).
I'd guess the mana cost of each would be 2XY where XY is their two colours. Indestructible seems like a given but I'm not sure how they'd work the devotion. Just thought some discussion on this might be cool. --- Psalm 27:1
Also I'm wondering if we'll see Phyrexian mana return, there's been a mention or two of "Devotion to Phyrexia" on Matt Tabak's Tumblr. Granted, he was probably kidding, but it works rules-wise and would fit very nicely into the Phyrexian theme. --- I have a blog now. I use it to rant sometimes. http://seabutcher.blogspot.co.uk/
I believe I read somewhere that Theros wasn't going to have hybrid mana costs, I could be mistaken though. Don't have a link either, unfortunately. --- Greatest STP of all time: http://i.imgur.com/niJah96.jpg
I'm expecting Devotion to Multicolor in Born, with Devotion to All in Journey. Perhaps a card that says you win if you have Devotion to All. --- http://4.bp.blogspot.com/-LU98ie6O7dI/Ufm0z4NvxSI/AAAAAAAAqOY/2MzHwcrn9o8/s1600/4+Ben+Askren+vs.+Andrey+Koreshkov.gif 3DS FC: 1590-5142-2689