I think some of you are missing the point. I'm not saying D&D as a whole shouldn't have all manner of wacky races and classes available, but to those of you talking about Arduin, what say we put Flying Sharks in the 5E core as a race?
I think you lost everybody when you disparaged dragonborn, tieflings and warlords as being too wierd for the core, but mentioned several classes and races that were just as fringe to many people (including me).
But this whole discussion is rather irrelevant. I get the sense from what was released at the seminar today that the 5e design team is following 4e's lead and proclaiming that everything is core... with the caveat that also none of it is. That's up to the group (particularly the DM) to determine.