So, first apologies to all, but I can't help myself...I'm an IP nerd.
Second, standard disclaimer: I'm only licensed to practice law in the USA, any information I give here is purely hypothetical, and do not follow any advice I may give without consulting a lawyer about your specific circumstances. Also, this is not to be taken as an agreement to represent anyone.
There, with that out of the way, most of GW's stuff would be classified as "Work-for-hire"/Corporate Authorship. In the USA, that carries a copyright term of 95-120 years depending on date of authorship and publication. After a quick check, in the UK that grants a minimum copyright term of 70 years. It can be longer depending on the authorship situation. So, to answer your question, we' re still a long way off from any edition of Warhammer being free of copyrights.