Also, on another note, an interview with Gamefreak led to a little more information being leaked. The competitively affecting news is as follows:
"Ghost-type Pokémon can freely escape from battle without being influenced by Shadow Tag."
"Some moves, with focus on special ones, have had their power and accuracy revamped."
And also possibly this : "The standard selection process for Pokémon Mega Evolution is based on three points: visual looks, popularity and game balance."
So to start off with the first one, we already knew that Ghost types could escape trapping moves like Mean Look and Spider Web (yes, that exists). However, this bit of news puts it into an entirely new light, as it can also escape the trapping ability Shadow Tag (I hear a Gengar gleefully cackling in the distance). What this means is that Ghosts will be pretty much impossible to trap, and those Levitate Ghosts are immune to every trapping method (as Arena Trap was not mentioned with Shadow Tag I believe). This will just make Ghosts even more overpowered than they are already making out to be, with Gengar being at the forefront of Gamefreak's oh-crap-what-have-we-done Pokemon this gen.
The next piece of information is actually quite interesting, as it means several moves (please include Focus Blast) are getting their power and accuracy adjusted, kind of like Tackle did this gen. This could open up a whole new realm of what moves are useful, but unfortunately there weren't any specifics so it's essentially speculation for now.
Finally, the piece of news that will somewhat affect competitive play I think is that it looks like there is only a selection of Pokemon that receive Mega Evolutions, unfortunately meaning we won't be seeing one for every fully evolved Pokemon. Adding this on to the complete embargo on Mega Evolutions for any 6th gen Pokemon, this means that it's likely we won't receive too many. It's also nice to see that Gamefreak is considering game balance when they make the Mega Evolutions, hopefully meaning that they'll make some more tank-like ones to compensate for these massive powerhouses they've been pumping out so far (well, excluding Venusaur).