Sure, go ahead and normatively reference 1.1, but please be sure to explain why 1.2 isn't being referenced. It would also be nice if words were included to explain what's needed to move to 1.2 in the future. In that case, maybe 1.2 should be listed as an informative reference.
I'm already dealing with someone who's complaining that the BEEP/SOAP RFC (3288) doesn't reference 1.2. I'd like to avoid having to deal with similar objections in atompub if at all possible.
--Paul Hoffman, Director --Internet Mail Consortium