It would be good to note the GT rules, which forbid the Empire any mercs except Giants (and that's probably only to support the kit). Based on that and the interview with Mr. McNeill (which implied that the DoW decision is either unmade or is as-yet unsaid by GW), it would appear that DoW are in something of a "Limbo" state, where the Empire can't hire Pikes but Chaos can still hire Cannons, based not on game balance or fluff, but simply on the order that the books are released. DoW armies are still completely valid, and I certainly wouldn't begrudge an opponent his Mercs in any friendly game, but the future is frustratingly unexplained. Perhaps DoW will be phased out as the books are released, or perhaps given their own PDF or book with full rules, but don't hold your breath for anything soon. For now, I think the best option is to avoid DoW in a competitive enviornment, where your opponent can point out that you "technically" no longer have the option for Mercs, and play with them all the more in friendly games.
On that note, however, I fully sympathize and agree with the massive confusion thus far from the lack of DoW in the Rare slot. My less-than-pressing question is, what about RoR? Many of them don't even take a Rare slot, using a Special instead? And there's nothing about DoW and RoR being interchangable terms - in fact, it's quite the opposite. So could I field Pirazzo's Legion but NOT a unit of standard-issue pikes?
Okay, I'm ranting, sorry. Anyway, my point was made up in paragraph one. In the interest of keeping this a friendly game, and not a competition-centered one, we should keep our wits and manners about us (as proper Imperial gentlemen) and aim to stay within the rules rather than pressing to the edge of them.
And yes, I'm hurt by the DoW situation - I have a converted unit of Ogre "Greatswords," complete with plate armour, straight-edged swords, and floppy hats with huge feathers that are sitting morosely on my shelf, wondering if they'll ever get to march to battle with Reikland again...