Agent Smith is right. It probably will happen sooner or later. (I vote for sooner) Actually, I've built some pretty complex things in Bryce, and mine are junk compared to what aother Brycers have done. I, and I'm sure they, would like to export their Bryce stuff.
And if you want the real reason that Bryce hasn't exported up to this point...if you were Metacreations and you sold Ray Dream as a modelling program, why would anyone buy it if they could make Bryce their modeller? You could at the time model almost anything in Bryce that you could model in Ray Dream and Ray Dream had some pretty annoying bugs that Bryce did not. Heck I did ALL of my rendering in Bryce.