Unless Sony are willing to adapt a similar concept that Warner Music & Rhino Records did with the Chicago Quadio box set, I think the only way we will see any Santana Quadraphonic mixes reissued is through Sony Japan on Multichannel SACD in the very expensive 7" packages.
The Sony Japan Multichannel SACDs by Jeff Beck and Santana were released in conjunction with upcoming tours in Japan.
So the real question, as it relates to more Santana Multichannel SACDs, is when will Santana be touring in Japan in the future?