Kay nobody is explaining, I won't waste time just to tell a genwun the whole thing so I'll make it short.
Mega evolution as a concept is being able to go past the pokémon's final form, it's one step more, You could it compare to SSJ2 in some way. To achieve said form you the pokémon can't work alone, it needs a strong bond with its trainer, underlining the whole human pokémon friendship concept.
Mega evolution are still mysterious though, for example it's also said that these forms, for some pokémon, aren't an actual step further to evolution, but an actual regression to their ancient state (Mega Aerodactyl).
In general the concept behind a Mega design is to further enchance a pokémon's capability, look at Mega Kanga, the kid'd desire to help the mom makes it grow and be able to fight alongside with her and become a fucking broken combination. Or look at Mega Hera becoming a Hercules Beetle. Sadly I said general, since I can't overlook that some megas are just "it gets spikier".
With ORAS we will have more explainations on Mega evolutions too.
Metagame wise they're an interesting concept to buff some pokémon considered useless before. (Kanga, Mawile, Charizard etc).
I wouldn't be surprised if one day every final stage would get a mega. It makes sense.
I have no idea what do you mean with "They run out of ideas". If they actually run out they're just pander to genwuns for quick dosh instead of taking one of the biggest risks they ever took just to introduce something new to the series. Since when trying to change path is called being out of ideas? If anything it's the fucking contrary.
Fuck this isn't short at all.
