No offense, i am not even a FF user, but this ideology does not go down well with me. Why not divert your resources to the thing in hand rather than spread out all over the place. A bird in hand is worth 2 in the bush.
Actually, they are not quite dividing the resources.
FF2 is already stable, meaning no development only bug fixes.
So no developers needed.
FF3 is now at beta 4 and close to being released.
Most of the work has been done and again only bug fixes to make it stable for the release.
It is at this point they start on a new version FF4.
And AFAIK FF3 Beta 3 itself brought native UI look to all three platforms.
Windows, Mac and Linux.
You should try FF3Beta4, seriously a lot has been changed.
And yeah even i hated the UI and if you thought the UI looked out of place on Windows , try looking at it in Linux where the windowish icons look terribly out of place.
But FF3 has now support for GTK+ on Linux and is looking way better.
Just give it a whirl and lemme know how you feel.