VDT was only moderately profitable (as blockbuster movies go), and both it and PC made way less than the first one. Producers don't look favorably on franchises with diminishing returns. There was also some disagreement between various involved parties about whether Silver Chair or Magician's Nephew should be next. Since they apparently couldn't reach an agreement and there wasn't a terribly strong financial incentive for the producers, it just never went anywhere.
Anyway, the production rights have all reverted back to the Lewis estate at this point, so if they were going to come to a deal with the same producers, it needed to happen years ago. Have you heard about the Netflix series, though?