I see no reason why EGSL was abandoned. It seems perfectly usable to me, provided you know what you're doing. And I think it would be perfectly usable for one or two game ideas I have, if coded correctly.
But, if YAB is the "future" of BASIC programming languages for Haiku, then I think we need to focus on promotion and more code examples. Really build up user awareness and an "experience" for it.
If the "Collision Example" I was working with, in EGSL, could be replicated in YAB, that would be awesome and would definitely spur my motivation towards using YAB.