Today, WotC announced the two potential sets of packaging for 'Action', the third set in the Scars block. A quick look at the art raises a few questions.
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Now, the first thought I had is all about the fat pack art for Mirrodin Pure, which clearly depicts Karn reawakened. Now, IF it wasn't just a spell and they decide to make him a planeswalker, I still doubt they'd ever make him colorless, or at least if he did his abilities would require permanents of certain colors (or permanents of no colors whatsoever).
The other showcase is clearly Platinum Angel, so nothing special there. The phyrexian art is harder to make out, as phyrexian art always is, but odds are good that the pack box art is for the Phyrexian Plaguelord that was the counterpart to Platinum Angel in WotC's design competition.
In any case, it seems likely that if the Mirran faction actually wins (unlikely from all I've witnessed), then Karn will most definitely be back in some form. For any more information, we'll just have to wait and see.