If it sold well, WoTC would be fools not to do more D&D sets in the main Magic releases. Hasbro has profit expectations.
it sold well, but it's to specific subset of people, mostly D&D & Forgotten Realms fans, not more traditional MtG fans. A product that does crazy well with a particular subset of the players is what Supplemental sets are for, Premiere Sets are for the broader fandom. Apparently Supplemental Sets can do extremely profitable as well, I mean the most profitable set as far as I know this year, was Modern Horizons 2, which surprised me because it's NOT standard legal and it's really mostly targeted towards enfrancised hard-core players and collectors and Varthos, not casuals many of whom are put off by the higher price (which admittedly was worth it)
Supplemental Sets also have ALOT more freedom in what mechanics and how many mechanics they use and mixing mechanics and reprints and how many Legends the set can have, and they can and often do have higher power levels.
I think a supplement that learns from AFRs successes and mistakes and takes the freedom and space that supplemental sets offer (such as Commander Legends, Conspiracy, Battle Bond, and Modern Horizons 1&2) to innovate can be vastly more profitable then AFR.
Here is a link to Mark saying AFR sold well.