I also tried to rise the problem of DA-aware observers before but never meet any understanding, and now we have 3 people, who seems to be speaking about the same thing.

We could name them (us) double-DA-aware-obserevers. That is the ones who know about DA and also know that DA is applicable only to observers, who knows about DA.

If we apply all the same logic of DA to this small group, we could get even worse results (and also go into eternal recursion). But it will not happened, as Carter in 1983 was part of double-DA-aware-observers, and it was 33 years ago. So even if number of double-DA-aware-observers is growing exponentially, we still may have 10-20 years before the end. (And it is in accordance with some strong AI timing expectations)

If one strong AI replace all humans or solves DA-paradox it will solve DA without total extinction.

I wrote about DA (for group of people who know about DA) here: http://lesswrong.com/lw/mrb/doomsday_argument_map/

It doesn't influence timing of the possible catastrophe much. Most people who goes deep in the topic have read (and publish) about DA. So we could use number of the articles about DA to get known distribution of DA-aware-observers. I suspect it is exponential. This means that the medium rank-number of DA-aware-observers are near the end of the time line.