I personally would wait to pot up in soil when there are a few more leaves on it just so you don't damage this frail little baby. Once it puts on more growth, you can transplant it at any time.
I've had mine crowded in a styrofoam cup for months and didn't lose any. But it also slowed down the growth because it had outgrown that cup! When transplanting, I had to loosen up the roots.
As long as the daylilies stay healthy (no root rot, pests, or diseases), they are pretty tough plants even as newly sprouted seedlings.
