No. Nukes will not require TWIC's. Nukes have nothing at all to do with transportation. The background investigation and clearance process required is a little more extensive. Nukes still require drug testing, psychological evaluation, credit checks, criminal record checks as well as the actual need for access (you need to get a job at a nuke before you can apply for a clearance - not so with TWIC)
A TWIC will never be sufficient to get a nuke clearance, and current access to a nuke won't make it any cheaper, quicker, or easier to get a TWIC - at least not for you and me, maybe for the government because you will have a file already open.
But, since you opened the subject, wouldn't it be nice if nukes would adopt the concept that one federally issued credential would be sufficient for access to all sites? Doesn't it make sense to not have to reinvent the wheel every couple of weeks?