I know conics are being worked on and I had hopes they might sneak their way into 2010 -- they have not.
I imagine a simple checkbox with the edge fillet options that says "conic" with a 0 to 1 value. That's it!
Though curvature combs like on boundary- surface would be nice for evaluation and perhaps have them run not on the fillet surface only, but also the supporting surfaces (same with boundary- too!) because it's the join there -- that's the most important.
And as my final plight, one could say a picture speaks a thousand words...