We learned about Smoke from the concept art on somebody's screen on the NRS website, but he was never confirmed. Nor was Quan, CSZ, or Sheeva. I don't think Kabal was mentioned either. Stryker eventually got a trailer, but I think it was the week of or the week after release.
Jade, Kano, Ermac, and Baraka turned up in other peoples trailers, but never actually got "revealed". Kintaro, Kenshi, and uh, someone else I can't remember were mentioned in a magazine, but there was still no footage of them until the game dropped.
Either way, both games had HUGE gaps of time with no intel. Literally, nothing. MKA was the last time they put together a website worth a damn, and MKvDC had MKasts to keep us interested but without Hans and Hector thats a dead deal.