It seems that the million-dollar question has a answer: «yes».
Watch the past and the present.
1.7 code -> Firefox 1 and Thunderbird 1.
1.8.0 code -> Firefox 1.5 and Thunderbird 1.5. (sunbird o.5?)
1.8.1 code -> Firefox 2 and Thunderbird 2. (and sunbird 0.7-0.8?)
So… 1.9 -> Firefox 3. Only.
There is an interesting disscussion in m.d.platform about that. KaiRo opened the pandora’s box 😛
I support Simon Paquet, another topic in m.d.l10n, about /l10n frozen for Ffb5.
Mozilla, don’t do that, please.