In spite of now being over five years old, both the PS4 and the Xbox One have been surpassing expectations and performing much better than expected in terms of sales. With the momentum that the two ageing consoles have managed to maintain, the relevance of traditional console life cycles has also been brought into question- despite that, though, the question of when the next generation of both consoles will be announced continues to be as pertinent as ever.
Recently, NPD analyst Mat Piscatella was asked on Twitter just how long he thinks the PS4 and the Xbox One can maintain their sales momentum, to which he replied that he expects to see a decline for both next year, before saying that that is also when he expects both the PS5 and the Xbox Scarlett (or whatever Microsoft chooses to call the next Xbox) to be announced.
2019 seems like the right time for an announcement for both. If 2020 is indeed when we will see the launch of next-gen consoles, which seems highly likely, it stands to reason that an announcement will be made in 2019. Just recently, in fact, rumours surfaced that Sony would be revealing the PS5 in 2019- read more on that through here.