Pepsi Throwback (and Mountain Dew Throwback) seem to have become a regular item on the shelves in my area of the country. Probably because sales numbers for the product have been fairly good. Supposedly it was only "for a short time" but it might also depend on the bottling company.

As for Coke, my understanding is that the only time they muck with the formula is when making Kosher Coca-Cola for Passover.

I'll have to look for the Dr. Pepper stuff, I live where two different bottlers both distribute Dr. Pepper (one's a Coke distributor, the other is a Pepsi distributor).