For new games, in the same way Mojang, Double Fine, Ninja Theory, Bethesda/Zenimax and Activision Blizzard announced their PS versions. Sometimes in their own channels, sometimes in PS ones if Sony still has some one signed.
Outside what Sony had signed before acquisition, I think they won't show stuff on Sony channels, only in MS/generic ones as could be the Doritos Summer Fest or Doritos Game Awards.
For ports of old games, I think they'll do it in a low key way maybe just posting a trailer and sending a PR release in a random day, or maybe in some generic event like the Doritos ones.