I hate to be the bearer of reality, but it's incredibly rare that Disney truly builds an entire parade from scratch. Even when a parade debuts all "new" floats, they're typically built on the chassis from older floats. Only when a park is getting a parade for the very first time, or when the design is a significant departure from the existing infrastructure, does an entire parade have new chassis.
The last parade built from scratch for the domestic parks was DL's Celebrate! A Street Party in 2009, which was structurally different than anything DL had done before, and its floats have been thoroughly repurposed since then. One of the stage units was given new life in DCA's Viva Navidad!, while the other 2 have been used for special events (one may have been repurposed for Paint the Night). The smaller 'balloon' floats were converted into the drum floats for Soundsational. And the character bicycles have appeared in parks around the world, most recently for a special event at WDSP.
Prior to that, the last all-new parades were Eureka!, Mickey's Jammin' Jungle, and Stars & Cars in 2001. Eureka! and Jammin' Jungle were the first parades at their parks (DCA and DAK, respectively), while Stars & Cars was a significant change from the traditional floats used at the Studios. Jammin' Jungle was largely abandoned, Stars & Cars was sent to Paris, and Eureka has been used to build "new" floats for Block Party Bash, Pixar Play Parade, and Paint the Night.
For most "new" parades they simply take old floats, strip them down to the chassis, and rebuild from there. Occasionally they'll be supplemented with floats from a different park (Festival of Fantasy's finale from TDL) or one or two truly-new floats due to a unique design (dragon), but the majority of the floats predate any given parade. Or has been the case all too often in WDW, they'll simply stick old floats into a new parade with some fresh paint and props.
So do I think that Disney ordered 50 new chassis? Nope. Even in the highly-unlikely event that they needed 50 "new" floats, the overwhelming majority of them would be built on the framework of what they already have. Why reinvent the wheel if you don't have to?