are there plans for a material browser palette in solaris where we can easily see previews of our preset materials and also see proper visual previews of new materials as we adjust the parameters?

any news on this?

As shown in the H20 keynote, the first part is there (in the material linker there is a "catalog" tab with a pre-populated set of materials). You can also create your own material presets.

For the second part, creating new materials and seeing the effect of parameter adjustments, I'd recommend using the new Solaris Lookdev desktop, and using the viewport for your material previews. May not be exactly what you were imagining, and it's not that we're calling this "done", but that would be my best recommendation given what comes out of the box right now.