After that logic would follow (i know GW and logic don't ever go in the same sentance) that next would be BT or SM. SW, IG and BA are all more competetive and newer than BT and SM. I suppose the argument could be made for orcs but that would be 4 xeno codexs in a row
I think you are going to see Orks before SM. After Tau and Eldar, Orks are going to be (and almost are) hideously overcosted in 6th. Especially with SM being a 5th ed Codex, it is looking like GW is trying to power out all the old 4th ed dexes first.
I bet you see Orks before BT since they have said that BT are getting a complete revamp ala Dark Eldar. Whereas Orks are a pretty easy update....change some points, jigger a few rules, give us cool new toys to buy.