I'm really surprised they haven't announced an Artillery Walker with the SSU now fielding a Command Squad and an Observer Squad.
As for the Widowmaker being able to damage walkers, I find it a little silly to think that their guns are any more effective than the Axis & Allies sniper rifles, or anywhere near as powerful as Angela's 20mm cannon. But then again, the USSR did gain some noteriety for using the PTRS/PTRD anti-tank rifles in sniper roles. Though these guns obviously take their inspiration from the post-war SVD.
Speaking of sniper rifles, the rifle squad scares the crap out of me. O.O
Also, I wouldn't hold my breath for the KV-152 guys. A heavy walker, perhaps, but something different. The KV-152 falls into the same category as Otto: despite any shiny new guns, it's still, ultimately, someone else's walker. For FFG to release such a walker into general sale, it would break down a lot of the visual differences between the factions. I just don't see them doing that, ever. For Dust Models, however, who deal in unofficial models that are rarer to find, something as realistic as a captured, repurposed walker makes sense.
Can't wait to see the new axis walkers too. And yes, my money is on the Wotan (Loewe on the schematics) PzKpfl III too.