I've not seen a 1/350 scale Vulcan shuttle, nor have I heard of one in-works. You never know, tho.
As to the Reliant question, Angry Wives Studios has a vacuum form styrene and resin details kit coming out at some point. No date set, but they're working on it, along with a 1/350 TOS Enterprise, Movie Era Federation-class dreadnought and Constellation-class (re: Stargazer). No release dates set on any of them. So long as they give a quality product that's as close to accurate as one can get, I don't mind if it takes another year. Quality over quantity any day.