My grape tomatoes have plenty of foliage, plenty of flowers and plenty
of fruit. Problem is...they're not ripening. The fruit still keep
a-coming, but even the first set haven't even started to "pink up",
and they've been on the vine for (literally) weeks. We've had lots of
sun and temps in the 80's.

Do I just need to wait, or is this a sign of some deficiency?

Mark

A watched tomato never ripens
Your tomato plant knows what it is doing so just be patient and let nature
take its course.