It did happen in the movie, and they actually remembered that Hibiki can breathe fire (Thank you Toei!)
And not to forget that during the first episodes of Hbiki, he also went Amazon on the enemies with his blade-claws, with "blood" spraying out and everything. No wonder Tsukasa used that form against Amazon in the movie. Its just a pity that it didn't happen in the show itself.
I wonder what happened. During the first half of this show, the writers actually made sure that the different Riders were used strategistically, and the new obtained Rider forms always seemed to match up with something in the next world. After Hibiki's world, it was more like:
Nega World: Lolz! Ryuki and Ryuga looks the same, let us use Ryuki!
Shinken World: uuuh... The writer for Shinkenger was also the writer for Den-O, let us use Den-O then!
Black RX World: No new ideas... hmmm... oh, how about this!: from now on we make a pattern, where the base-form of the Rider that Complete Form will summon in the next episode will be used in the first episode. Brilliant!, so what are we using next episode? Shining?, okay, then we will use Agito in the first ep.
Amazon World: Faiz Blaster next ep? Okay, then we use Faiz in the first.
The ONLY practical use I have seen of the Rider forms lately was when Tsukasa used Ryuki and the Mirror World to ambush Apollo.