Its still rumored that the Space Marine Command Tanks models exclusive to Warhammer World will be in the new codex. Its hard to tell at the moment whether this will happen or not right now, but the rules are at least out there for people to see and read.
Leaked Images are out there, so if you are interested in checking out the rules for these guys... Here they are.
via a reader on Faeit 212
http://boards.4chan.org/tg/thread/40320964/space-marine-command-tanks