I would definitely want to see some new Ura characters of any capacity - there are a lot of things they could do with the concept. Plus, seeing the older Ura characters get their personalities improved on would be awesome.
As for the Ura characters not yet appearing in the anime, keep in mind that Ura Tamatown is actually inside the Tamagotchi planet (Via the mouth!) and not on the surface, so more than likely if they do appear it will be in a special one shot episode or something among those lines. Even then, I doubt the regular characters will appear alongside them right away, unless they figure out a plot that would work for that to happen.
Fun fact... the Ura concept was more than likely inspired by a similar concept in the Digimon series, the X-Antibody, which was introduced prior to the Uratama's release. In Digimon's case, there was no outline color change and the physical appearance of the regular characters who got an X variant changed much more drastically than a Tamagotchi who got an Ura variant.