I understand why the Kobold will likely never get a true "official" PC-adaptation, but I'm still kind of disappointed. The MM writeup feels like a tease...
I think one of the problems with Shifty is that it's pretty situational. Compared to the best of the racial Encounter powers, I don't really think it's completely over the top, but it is abusable and something that I think the DM needs to keep aware of when designing encounters, etc. There's a number of other powers / options in 4e like that, but I don't think that adding more is a casual decision.
I see the main advantage of Shifty being able to shift two squares per round, every round, plus a standard action to attack. Someone mentioned ranged attackers benefiting from it, but I don't seem many situations where you couldn't do as well shifting as your move action. It does introduce the possibility of selecting away from other movement-granting powers, but I don't feel like that's a good option, IME.
Limiting Shifty to once per encounter, OTOH, seems really incredibly weak. Possibly adding in some other bonus / adding more utility to it might help. I'm not really sure where to go with that (and it would be better discussed in House Rules, I guess). I think that right now Shifty is at least partially balanced by the lack of any racial feats for the Kobold. I think that finding an overall direction for Kobolds as a PC race would help define what was a good option for Shifty. But I'd be wary of creating a situation where the PC version of Shifty was only good at the cost of a "feat tax".