I was having a conversation with a chap (staff member) in the local GW about how I am making an Adeptus Mechanicus Army from scratch, conversions of servitors, bionic limbs for Guards etc.
He told me not to bother as the strong possibility existed of an AM 'codex' and dedicated AM range of miniatures in the 'future'.
Now as a former staff member myself I know that rumours like this are often wishful thinking, occasionally blatant rumour-mongering by head office to mess with people's minds.
But that is what he said so take it however you will. He also said the next few codices/armybooks were decided and that AM are not amongst them (Ogres, SM, Tyrannids I suppose then some more popular ones like Eldar then who knows..).
The next suggestion was that next years summer campaign (and I rarely subscribe to SCs so I have no opinion on that opinion) is going to be nothing to do with 40k but that the year after that (errrr) 2006 might be of interest to a man of the world like yerself (nudge nudge wink wink etc..)
I really really doubt that Mars will leave the Imperium wholesale. Fluff wise, the techpriests of the AM are all that keeps the rotting technological base of the Imperium going and by changing that realtionship you change the whole nature of the Imperium. To be honest it is a change that I wouldn't be keen on and probably wouldn't follow.
They wouldn't do it infact, they might involve the Dark Mechanicus a little as badguys maybe but I suspect that the bulk of the campaign (if it actually happened) would be Necrons vs Mechanicus and Imperials on Mars.
Possibly fluff involving a failed coup by supporters of the Machine God after which a Necron Army arises or arrives on Mars with the intention of liberating the Dragon.
Iron Hands going rogue I can't see. Killing a special character in a campaign is no big deal but changing the allegience of an entire army (in game rule terms I mean) I would doubt. People play the Iron Hands - you can't just explain to them "oh and by the way, you are batting away from now on" it wouldn't wash fluff or playerbase wise.
But as always I stand ready to be corrected, by those with better thoughts on the matter..