If you're expecting a slew of MCU updates to follow the releases of Spider-Man: Homecoming and Thor: Ragnarok, you're going to be sadly disappointed. According to Kevin Feige, the studio are withholding as much information as possible until after Avengers 4 comes out - presumably to preserve the secrets of that arc-ending event, but also to focus attention there.
We already know that the third Guardians Of The Galaxy movie will land in that "phase" - even if the phase format itself is dropped - and that a Doctor Strange sequel and a Spider-Man sequel will also drop, but beyond that, it remains pretty vague.
And in an interview with io9 while promoting Homecoming, Feige confirmed that there won’t be any announcements about what follows Avengers 4 until that film is out. Or at least he hopes so.
“I hope [the news comes] after that. I think there will be certain elements that start to come about, not the least of which is the already announced release date of the next Spider-Man film. But other than that we’re going to keep it very close to the vest because this is really about focusing on the unprecedented conclusion to a 22-movie overarching narrative.”
It's unlikely that will fully be the case: by the time Avengers 4 comes out, Marvel will already be working on the films that follow it (especially as Spider-Man 2 comes out shortly after it) and keeping them all secret will be nigh-impossible. So it might be that the studio goes with a couple of the known Phase 4 movies first, and then announces the second wave after Avengers 4.
Indeed, Feige also told the junkets that Spider-Man would "lead" the next phase:
“So much happens in [the 3rd and 4th Avengers movies], as you can imagine, and so much is affected by it that we felt what better person to hold your hand and lead you into the next incarnation of the MCU, in a grounded, realistic manner, than Peter Parker? So, coming out two months after Untitled Avengers, [that’s what] much of what the next Spider-Man film will be about.
It was purposefully done like this. Like how the events of Captain America: Civil War impacted Peter as he was dropped off by Tony and expected to go back to continue his sophomore year, how the hell are the events of Infinity War and Untitled [Avengers] going to affect him as he, yes, goes back to his junior year?”
Perhaps we'll end up seeing the rest of the post-Avengers 4 movies announced in the build to Homecoming's sequel release, assuming there's already a couple of other movies officially green-lit by then...?