Rubicon will be releasing a T-26 soon, and that has got some people excited, but as for IS-2 or KV-1/2 kits, I would rather see Rubicon release something that no one else has done yet. The Italeri KV-1/2 model kit is not perfect, but its a pretty good kit nonetheless. Same goes for the Italeri IS-2 model kit, though, to be honest I have not assembled the IS-2 that I have, but the parts look good.
Instead of Rubicon duplicating what Italeri has already released, I would rather see Rubicon release something new like a SU-76. I think it would sell a lot better as well because no one makes a 1:56 scale plastic kit of the SU-76.