What I am suggesting is that the community from which the Revelation prophecies emanated was already in existence in the 50s and that already at least some of its members were prophesying an end-time reign of Christ on earth. Many mainstream scholars agree that the author of Revelation brought older oracles into his work and incorporated some of them with little or no alteration.
And so Earl Doherty:
it is folly in itself not to regard this discussion as directly relating to the dispute with Apollos.
During the mid 50s, there existed already a Christos movement, in a number of communitities where such beliefs were already current. Paul and others knowingly engaged these Logos-Christos Gnostics, knew their points, and spoke their language in 40 AD. What presupposes this Judaic Gnostic intellectual milieu was novel? Within reason, it was at least a generation old (c.20 AD) confirmed: from Philo Judaeus c.35 AD, we know there were many such heterodox, radical allegorists preaching what Philo considered heresy. (From a tradtional Palestinian Jewish standpoint, Philo's own Logos Doctrine c.25 AD was pretty far out-there too; he doesnt elaborate his opponents' most radical ideas, so he must be considered 'conservative' among a wide spectrum of Allegorists.)
On the Christos Doctrine itself, Apollos' Epistle to the Hebrews (Melchizedekians = Alexandrians) shows the Christos-Logos doctrine was fairly recent c.50 AD and unfamiliar in the great metropolis, so arriving c.40-45 AD. Where does the Christos Doctrine originate? Alexandria had just suffered an enormous (the first recorded) progrom - the Jewish community was devastated. I highly doubt this idea begins in Jewish or Gentile Alexandria so late: the Christos Doctrine is probably Phoenician or Syrian in its oldest form(s).
(Proto-)Gnosticism is a different, much larger topic: it is likely to have emerged in Middle Egypt c.100 BC onwards. (Very fuzzy.)
The pressing need for personal salvation and dire forecast behind Revelation prophecies are different but related strands in this weaving. Paul had studied this kind of material, knew how to answer and mould listeners' expectations on familiar religious & philosophical terrain, as he preached in heterodox communities and radical synagogues which were already in existence c.40 AD. Paul's message was not entirely new-new in all its particulars, the ground was tilled.
In coastal Asia Minor and cities where Paul worked, these Judaic communal beliefs included foretellings of palingenesis, a Destruction of Reality and Cosmic Renewal. (The destruction part had just happened to Alexandrian Judaism in 38 AD.) Classical Gnosticism is characterized by an Evil/Furious Demiurge: as when God flooded the Earth to wipe out Mankind. So next time, with Fire? (Evil Demiurge, check! Definitely 'Gnostic'.) These "older oracles" were two or more generations older? Therefore, we are talking about Gnostic/Apocalyptic teachings found in Asia Minor by at least 25 BC, if not much earlier.
It seems probable that radical 'Egyptian' (Alexandrian Jewish) teachings radiated out to the Diaspora for generations before Christ, but there's no reason to assume Alexandria is where it all began. The ideas came to Alexandria from the hinterlands, found translators, and transited the metropolis via trade-networks to the coastal cities of the Eastern Med.