Hi wmkr,
Because Pearl rays can change both pattern and base colour over several years it is never 100% that a light base pup will remain that way indefinitely, I have had dark based pups change into light base within 18 months and vice-versa. At the end of the day a good dark base looks every bit as impressive as any light base I have seen. Where ever possible seek out the parents of any pups you are about to purchase, this will give you a fairly good idea of what to expect from your pups once they reach adulthood. Having said all this I do have 2 female Pearls that kick out lighter pups consistently and one that turns out a darker form, I would never guarantee they will remain this way however, experience tells me different.
I can add some examples to this thread of light base pups I have produced over the years if you would like to see them?