Hi, Gary--
By mid-March, the number of rosy-finches and the sizes of individual flocks will start to decrease. Some species may depart earlier than others. Since Gray-crowned Rosy-Finches have been scarce this year, I would not be surprised if they become harder to find.
However, flocks have persisted past the middle of March in 7 of the past ten years, and stragglers often continue into early April. All in all, you have a fairly good chance of seeing all three species, and an excellent chance of seeing at least two.
See the charts and links to earlier years' sightings logs on this page.