Hmm I'm thinking it would be pretty interesting if twilight realised her potential and become one too so there would be 4 Luna the magic of night celestia magic of the sun cadence the magic of love that keeps the harmony and balance, with twilight the magic that unites them all together (her talent being magic and her name well being twilight and the fact she kinda brought Luna and celestia back together ) I dunno that's my theory Pretty pic too btw