Fear not - I predict that the Duchess will blossom into a jewelry hound eventually. For now, there is clearly a strategy in place to ease her into official life slowly - especially while William is still in the service. Part of that is obviously limiting her official engagements, but another part may well be limiting her adoption of traditional royal trappings. Not to mention, she doesn't exactly have a full jewelry box yet. Once Wills is out of the service and the couple begin full time royal duties, the sheer number of receptions, banquets etc. she'll have to attend will just about force her to accessorize more than she does now. So I bet we'll then be marveling at the jewels that begin appearing on her.
That said, given her tall yet slight frame, and her natural modern style, I would also bet she'll lean toward smaller, simpler pieces (more Princess Anne and less Queen Mary / Camilla). But that may allow some of the smaller, simpler jewels we haven't seen in a while to emerge from the vault - or maybe even some new commissions.
The wedding tiara will no doubt reappear, but I also continue to believe that she will also appear in the Lover's Knot tiara at some function within the next 12 months. She almost has to! I mean, the Queen won't wear it, Camilla will NEVER wear it, so unless it is given to Kate, that beautiful tiara would have to sit unused for the next 50 years. Unthinkable.