I'm almost sure Xerneas and Yveltal, and possibly Mewtwo, will NOT be in ORAS. The picture shows X and Y as well as ORAS, so it could just mean all the ubers that are collectively in all games announced so far. Zygarde, Rayquaza and Giratina are absent, though we all know Rayquaza will be in ORAS. Then again, Xerneas and Yveltal are on the side of their opposite games, which could mean something.
If past remakes are anything to go by, then the remakes tend not to feature the ubers released in their generation. FRLG didn't have Groudon/Kyogre/Rayquaza, and HGSS had all three but only unlockable by event, and you could choose only one. Considering GF loves trading, it would be against their mindset to feature Xerneas and Yveltal in ORAS, effectively rendering X and Y useless.
I do believe the list is accurate, though, because to the left are all the legendaries that appear in the "first" versions (Ho-Oh, Groudon, Dialga and Reshiram) and to the right, the ones that appear in the "second" versions (Lugia, Kyogre, Palkia and Zekrom), which is consistent with OR being the first version and AS the second.