Curtis Mayfield's Curtom catalog was bought by WEA in 1996 so all reissues are through Rhino and therefore this is a question for
@ForagingRhino .
Whether the quad masters still exist is another question altogether - when Mayfield still owned his own tapes he stored them in his basement, and many of them were apparently destroyed in a fire sometime after the 1990 stage mishap that resulted in his paralysis, according to a quote from his daughter in his biography:
"
Altheida bore much of the brunt of caring for my father. Home healthcare workers came to ease her burden, but she still worked herself to the bone. One night, exhausted, she put a candle near the wall and forgot it. The wallpaper ignited. Soon, flames engulfed the second floor of the house. They had to evacuate fast, wheeling Dad beneath billows of black smoke and deadly fire. He watched his home burn, knowing if no one had been there to save him, he would’ve burned with it.
Dad kept his old master tapes in the basement, and when the fire-hoses extinguished the blaze, they also doused some of the most famous recordings in soul music history. I went back and salvaged everything I could. Some tapes survived, and I began the process of digitally remastering them, culminating in more than fifteen reissues from the Curtom catalog on compact disc. Many tapes, however, we lost forever."
There are still a few of Mayfield's lesser-known '70s/early '80s albums that have never had a digital release from a tape source. Charly Records in the UK seemed to have some kind of grey-market rights to the catalog but no access to master tapes - their releases were either digital clones of US and Japanese releases, or needledrops of crappy-sounding LPs.
The phenomenal-sounding 2019 box set
Keep On Keeping On: Studio Albums 1970-1974 is the first time that
Future Shock (the better of the two Curtom quads mix-wise) has ever had a digital reissue from a master tape, so maybe there's hope that the quad mix exists as well. Both quad mixes aren't really showstoppers (they're like the Al Green and WAR quads, mostly double stereo with some elements pinned exclusively to the front or back) but certainly worthy of reissue if the tapes exist, especially given the scarcity of good-sounding tape-sourced reissues in the digital age.