Greg Egan was lampooning them in Zendegi and Schild’s Ladder for what is worth, and also Crystal Nights contains the following banger:
You know what they say the modern version of Pascal’s Wager is? Sucking up to as many Transhumanists as possible, just in case one of them turns into God. Perhaps your motto should be ‘Treat every chatterbot kindly, it might turn out to be the deity’s uncle.’
Interestingly, the posthuman worlds in some of Egan’s books do resemble longtermist wet dreams somewhat, the crucial difference being the lack of superintelligence.