Someone on BoLs is suggesting that this:
means there is a plastic version coming soon. You can phone Forge World and ask yourselves! Two of the Bunnies have and we both got the same response:
The reason that the Rhino is unavailable is because they are changing the product code. This is because all their tanks are being moved over to boxes instead of bags. This will affect the last 4 digits of the product code. It should be available in a few days.
Furthermore (and this is just my opinion folks) Forge World is aware of what Games Workshop is releasing months in advance, I believe they would of held off releasing the new command tank if the plastic was coming so soon.
So, although I think it's more of a 'when' situation than an 'if', I think that a plastic Deimos is still a way off.
Hope this clears it up a bit :)