Unlike others (namely I-795), this one makes some modicum of sense. Given the high unlikelihood of US 1 ever being upgraded to freeway north of Raleigh, this provides an Interstate connection to/from points north on I-95 to Raleigh...a function similarly covered by I-40 for points south.
True, the shoulders may not be full-Interstate grade, but NCDOT would have to remedy that before they could sign it as I-495. As for the Nashville bypass, the original part of the bypass dates to 1963. It was originally a Super-2...I'm not sure when it was 4-laned, presumably sometime in the mid to late 70s when much of today's freeway between Eagle Rock and I-95 was built.
Since nothing has come through AASHTO's special committee on route numbering as of yet, I presume NCDOT is planning on submitting this to AASHTO and FHWA in the not-too-distant future.
It should also be noted that, if this were to go through, it would theoretically enable NCDOT to renumber I-540 to I-640 as it would then connect to two Interstate routes. Bob Malme suggests as much on his NC Interstate page that SPUI linked to.