I think there will be a Mega Swampert and Mega Sceptile because Blaziken already got one :3
And Charizard has 2 Mega Stones while Venusaur and Blastoise only have 1. Just because they are all starters doesn't mean they'll all get Mega Evolutions. Only 4 of the 18 have Mega Evolutions and it may stay that way for a while.
From the ONM:
There's a reason for this biblical tone, readers - the Pokemon Company has announced that the much-requested remakes of their GBA games will be arriving in November under the names Omega Ruby and Alpha Sapphire.
Unless the ONM isn't "official"...
Only "Official" sources are Pokemon.com and Gamefreak/TPC themselves. Unless the word is from one of those sources, its not an official source.
They are officially stating: "Pokémon Omega Ruby and Pokémon Alpha Sapphire are a fresh take on Pokémon Ruby and Pokémon Sapphire, which launched in 2003 and were fan-favourite hits on the Game Boy Advance system. The new titles promise to take players through a dramatic story within a spectacular new world."
Dissecting it a bit:
A Fresh take on Ruby and Sapphire. A "Fresh Take". Its not the same story. So from beginning until the climax they are saying the story is itself is new and different from what Ruby and Sapphire was. Amount of differences remain to be seen, but the theorized "Sequel" to the new rumor about it being a completely new game seem supported by this small phrase.
"The new titles promise to take players through a dramatic story within a spectacular new world."
A Key part of this paragraph. The highlight is at the end, spectacular new world. They did not refer to Johto or Kanto as new worlds when those were remade. This is a pretty good hint if any that there is a chance we may not even be in Hoenn.
We could be in a new region, with a Hoenn like story. So the Aqua/Magma rivalry could be going on, with a new focus on the new forms for Kyogre and Groudon. Perhaps another region where they rest after their fights. While the games share the old titles, they don't have to be of Hoenn. We'd definitely need confirmation that we're in Hoenn for the new games since they aren't being treated as remakes by the company from what's being said so far. We could be in the mysterious 7th Region that was blatantly hinted to us by Gamefreak through use of an Easter Egg. While there were direct information about Hoenn and its events in X and Y, there was one NPC that said he was from another region that was soon to be revealed to us. Now we have two new games that may or may not be remakes.