Markezich & Valby both have more to give in the 3000, IMHO. How much more, I don't know.
Markezich's 3000 PR is 8:40.42 while Valby's is 8:42.29. I once read somewhere that a 3000 Steeplechase time is probably equivalent to what one would run in the 2 mile. If that is entirely accurate, I am not sure. I don't know how that figure was derived or where it came from. Markezich's steeple PR is 9:17.93 so if that conversion is accurate, that would put her 3000 time in the ballpark of 8:36ish. That seems reasonable to me. The steeple time was from last July and Markezich seems to be in great form now so it would not surprise me at all if she is capable of getting close to 8:30 or, at the very least, under 8:35.
It will be a good one.