Before Origins was revealed at E3 last year, there were rumours that the Egypt game would be the first in a connected trilogy that would cover Egypt, Rome and Greece
https://www.mcvuk.com/business/leak-suggests-assassins-creed-origins-is-set-in-egypt . Assuming that is true then the 3 games could show the various influences that made the Assassins order what it is, with the Rome one tying it all together.
Then after that hopefully they will give the series another gap year before the next instalment.
That said, in many of the interviews with the Odyssey team they mention working with the Origins team to work out how to take the series forward - either they are playing their cards close of their chest, or there is not another team working on AC to produce the Rome game, whether that means there is not a 3rd game or that we'll get the 'gap year' before it arrives.