We are well aware of the delays in the Firefox/Gecko releases. We are
currently assessing and thinking about the remaining schedule for TB 3
(we've still got another beta in between don't forget).
What I can say is that we will be releasing on Gecko 1.9.1 - to move
backward to 1.9.0 would be too much work, to move forward is definitely
not an option.
We could release on our own version of 1.9.1, but then we would be
responsible for porting and maintaining security updates rather than
piggy-backing on the Firefox core security updates. Although if it was
sufficiently close to Gecko 1.9.1 final, there's a chance we could do a
point release that would be the same as 1.9.1 final, but that would be a
risk, especially to extensions. So we have some careful thinking and
planning to do.
Over the next couple of weeks we'll be putting a plan together for post
beta 3 activities, and will announce more as we finalize the plan.
Standard8
And note that Thunderbird's "last beta" is currently scheduled for a
later date than Firefox 3.5's "last beta", so if it takes a similar
amount of time to go from the last beta to the final, Thunderbird 3 will
be after Firefox 3.5 anyhow.
That said, we know that we already have delayed the schedule for both
Thunderbird 3.0 and SeaMonkey 2.0 on our own terms and independently of
the delays in Firefox 3.5 and we all should really try to get those
releases wrapped up soon.
Robert Kaiser