Perhaps you'll meet the warden, but they will be fully armoured. But that means DA Keep would need to allow you to at least choose a race and gender for the Warden and at that point why not just let us create the full character.
I expect the Warden to be talked about a lot, but never shown. Regardless of what BioWare have hinted at. I imagine it's meaningless teases.
I fully expect the Keep to track things like race and gender, appearance is a lot more complicated than just some check marks for whether you did x or y, still unfortunate though.
As for the Warden appearing in the game I expect it should be somewhat substantial. The lead writer has made a couple of statements on how they aren't going to include things like the Dark Ritual or bringing back the Warden or Hawke unless they can do it right and in a meaningful way, otherwise it's pointless to have a cameo or some simple shit since you'll just be disappointing the people your doing it for since they're the only ones who will understand it or see it. So you either do it right or not at all.