Well, rationally, I'm hesitant to jump on to the "all these Hoenn events means remakes" bandwagon, however, in Groudon/Kyogre's case, it's to celebrate the 10th anniversary of RS being launched. I do hope they do an all new adventure though, in the Hoenn, since Team Magma/Aqua are a bit dated, and now in the whole Pokémon timeline we're years past when the events of RSE took place. Nontheless, if Gamefreak follows precedent with the previous remakes, it stands to reason that they are on the way (and hopefully not 3DS based).
Anyway, Mat believes that they're going to use their current engine at least once more before shifting to the 3DS era.
As for Jirachi knowing Psystrike, odds are they'll give it another useless move, or Psycho Boost (yay Specs set).