I think that's actually what's canonically going to happen. There have been a lot of hints.



For example: compare all of Cinder and Pyrrha's outfits. They've got some _striking_ similarities. Their colors are both red and gold, they both wear earings and a collar, have bare shoulders, upper back, and upper chest, cover their arms above the elbows, have a trailing bit of red fabric coming off their right hip, and wear dark heels. Cinder's flashback outfit especially is very similar to Pyrrha's outfit. Pyrrha's ball gown is nearly just a full-length version of Cinder's usual dress, being a crimson dress with bare shoulders and back, a slit up the right side, and an asymmetric hem. And Cinder's ball gown, although only briefly seen, seems to just be a black palette swap of Pyrrha's ball gown with the exact same pattern and a pair of gloves added.



And that's just their outfits! There's so many things suggesting that they're thematically the same character. Pyrrha's first name literally means 'the color of flame'.