The way I expect this to play out is for the full circuit to rule in favor of Judge Sullivan. When Flynn's lawyer appeals to the Supremes, they will refuse to hear it and that puts Flynn back under Sullivan's control. Sullivan will give Flynn a sentence of about 3 years, which will force Trump's hand on a pardon.
My guess....Sullivan will suddenly retire. You think all those judges will go out on a limb for Sullivan. I don't think so.