I get that there will be no more updates, but are they still going to take feedback from the forum and make some subtler changes?

They mentioned that we should still continue playtesting and submitting our feedback. I think they'll be making some more changes to the rules through the rest of the development process, even if these changes don't appear in a PDF update.

What? No more updates? Where does it say that update 6 is the final one?

From the description on the announcement:

"Greetings Acolytes!

This sixth update is the final one for the Dark Heresy Second Edition Beta testing.

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While this is the last update (pdf, 4.8 MB), there is no reason for you to stop sending in comments and test reports—especially for areas of unclear or contradictory rules."

Hadn't noticed that second part.