Although not officially confirmed, it is a high chance that the shiny rate in the Friend Safari has increased.
Many people are talking about their new shiny that they got in the Friend Safari, some even stating that this was the first shiny they got in the whole game, let alone their whole life as a Pokemon player.
It is most likely increased, unless the millions of people playing X and Y right now are just having amazing shiny luck. But rest assured, it's probably increased.
Hope I helped. :)
Source: Internet... xD