Since it's a modern action film that's supposed to appeal to the youth demographic, while also at the same time meant to be the start of an interconnected cinematic universe, of course POWER RANGERS will have an after-credits teaser. It's, like, Hollywood law at this point. I'm pretty sure directors who don't do it are drawn and quartered.
Anyway, speaking with Collider, POWER RANGERS director Dean Israelite had this to say about the after-credits scene:
There was always going to be a post-credit thing. The only question was whether it comes 2.5 minutes into the credits, or right at the end. We decided to break (the credits) up and go 2.5 minutes in. It felt correct.
While there's no clarification in the quote itself (besides the existence of an after-credits scene in general), many rumors have indicated that the teaser will indeed tease Tommy Oliver, a.k.a. the Green Ranger. Which, honestly, seems like a no-brainer. I mean, they could zag us and reveal Zedd or something, but since Tommy is like the Wolverine of POWER RANGERS, to not mention him at all seems foolhardy (though I agree with not fully introducing him until a sequel).
Either way, POWER RANGERS will "GO, GO" and morph into theaters March 24th, 2017.