The Retro Roto line was in full swing by 2006, and Jazwares -- looking to capitalize on Wave 1's success -- sought the production of special Halloween themed variants. The line would have been exclusive to specialty retailers like Hot Topic, but those plans fell through. Citing a lack of interest, Hot Topic and the like simply didn't want to stock 'em.
But there's more to these toys than meets the eye: they glowed in the dark. However, the gimmick wasn't enough to make retailers budge; ultimately, they were cancelled. Rumor has it Jazwares tried again the following year, pushing for a nation-wide retail release. As you no doubt know, nothing came to fruition.
It's a shame these never launched. We could so totally use more spooky-themed Mega Man goodies. That and they would've for an excellent collector's items! Alas, Jazewares prototypes are extremely difficult to come by this day and age. Chances of coming across these guys are slim to none. But I'm not a fortune teller: perhaps one day, a former Jazwares employee will sell some unproduced stuff via auction. Until then, we can only marvel at what could have been.