My wife and I took one of our famous road trips up to the mountains this weekend, and as such I can confirm that "FUTURE I-42" is fully signed between New Bern in Craven County all the way to I-40 in Wake County, in both directions-complete with "BEGIN" on US-70 eastbound approx 1/2 mile east of I-40 and "End" approximately the same distance from I-40 on the westbound side. What I mean by "fully" is that NCDOT has placed the 2 signs per county that they bought out in the field.
I have not been east of New Bern to see what they did in Carteret County, so I can't speak to what has been done down that way, yet.
I have noticed, that all but one westbound was placed on an an existing freeway section (and now I forgot which one wasn't on a freeway section).
It was after midnight when I was coming back eastbound so I forgot placement on those for sure but I want to say all were on freeway segments.