I asked my contact at Waves about the plans for S6L and at this time they are only able to say exactly what the press release says -
"The Avid S6L will have Sound Grid compatibility"
The whole deal is probably just far too new to say anymore - or commit to how it will work. WRT to connecting via MADI - this is a straightforward SoundGrid connection today for any MADI system. AVB has been in the plans all along but where it stands on the overall schedule I do not know. Rednet integration (while certainly possible) is something I have no knowledge on.
I would love to see AVID/SoundGrid integration go far beyond S6L but at this time we have no idea what might happen. A control surface/console that is natively aware and actively updates StudioRack configurations would huge (to me)... I look at DigiCo and wonder