The Darrow ending cannot be canon, because human augmentation is alive and well in 2052 in Deus Ex. Many of the major players in the Illuminati are present in Deus Ex, like Bob Page, Morgan Everett, Joseph Manderley, and the DuClares, so the conspiracy was not uncovered.
The Sarif ending cannot be canon, as Eliza Cassan says it will eliminate public hatred of augmented people. However, 15 years later, in Deus Ex, there is still heavy prejudice against people like Gunther Hermann.
The Taggart ending could possibly have happened. It places heavy government restrictions onto human augmentation. In Deus Ex, the only groups that experiment in augmentation are the Illuminati, MJ-12, and VersaLife, all of whom have government connections.
The fourth ending is the most likely scenario. Sariff, Darrow, and Taggart would all have continued to fight for their causes between DE:HR and Deus Ex had they been alive. There is no mention of them in Deus Ex. Had Darrow survived, one can assume he would have attempted to get the word out about the Illuminati. The conspiracy only grows more powerful between DE:HR and Deus Ex, so the ending in which Panchaea sinks is probably the canonical ending.