The old 5th edition rulebook is now no longer available through Games Workshop online retail. This can only mean that the 6th edition will be on its way very soon. Coupled with the rules in White Dwarf about the flyers, new chaos marines, Dark Angels on the spine of White Dwarf (etc.): there's a lot of change in the air at the moment.
The snippet of information that I've been liking most is the possibility of flamer weapons setting alight scenery pieces. Although there have been some arbitrary rules about things like this for some time (cf. the Battle Missions book), having this canonised in rule form for all to have access to is good. I'm hoping the flamer will become a tactic in its own right: multiple units of chaos marines that really are making the galaxy burn one building at a time! Consider this: units of chosen advancing behind a screen of flames until they're ready to unleash some hidden power weapons... well: I can dream anyway.