I support Dislestia as a past relationship, but not a present one. I think it'd be a fun explanation for a lot of Discord and Celestia's interactions. At this point, however, I don't think a stable relationship between the two would ever be possible.
Fluttercord, though? Praise be to Celestia, this ship has sailed as my official OTP as of the S4 finale. I didn't ship it at first, and just found Discord's inability to convert Fluttershy to be funny, but then season 3 rolled around with "Keep Calm and Flutter On" and found it cheesy, but cute. Honestly I didn't really start shipping it until season 4, since Discord showed up a lot more, but the premieres, "Three's a Crowd" and the finale all displayed their chemistry really well and wow, what dorks. They're adorable