Let me put it this way: there isn't a shred of difference between their admins and ours. They don't know anything more than us, there is absolutely no difference between the people who made that wiki, update it and the people who just read OP each week.
Ironically enough many wiki mods annoy me. I once added something to the OP wikia, which then was removed for some reason and I once saw an argument on the Avatar: TLA/LoK wikia about the opening scenes of LoK where they didn't want to acknowledge that the airbender in the opening scenes was a grown up Aang, even though it was fairly obvious, till a grown up Aang was shown in the series.
They pretty much got double standards on all these wikia's. People add stuff mostly from a subjective point of view, but they want to deposit it as being objective. I also notice that when people make RP bios where they copied a lot of stuff of Narutopedia, character are completely milked out so that even the tiniest detail sounds important.
It's highly unlikely that Doflamingo is really dead, so the most logical approach would be simply say 'presumably deceased' or just nothing at all till there is some clarity about the situation, but they want to update everything as soon as possible, but on the other hand want only to provide the 'truth'.