Is it possible, or even likely, that some of these characters will be fleshed out more in the future books? Of these characters the only one I feel truly needs more character growth is Lyanna Stark, and I find she is also the most likely to gain more book time in the future with Jon inevitably learning his true parentage.

Some of them, certainly. I agree that, what with Bran Stark’s time-travel visions, we’re likely to learn a lot more about Lyanna Stark, but I think there are opportunities for others (Stark ladies especially from his visions). Jaime’s already had one dream about his mother, so there’s no reason he couldn’t have others. We could learn more about the Princess of Dorne from some Dornish chapters, etc. 

Or…this may be where Fire & Blood (or the equivalents for the other Houses) and/or Dunk & Egg can really help, allowing for enriched world-building without slowing down the main narrative.