We don't even have the Future Exit #'s for I-99 along US-220 yet, and those have been posted for several years.
If we're going to do this, we somehow need to recognize that they are indeed I-99's #'s by maybe making the labels in the 'FI-99(#)' style like on the segment of US-74 in NC. But then again, that case only arised because NCDOT was forced to pull the I-74 shields down, and we had already incorporated the new I-74 exit numbers into US-74's file.