Question

Was there any change in the shiny encounter rate in ORAS?

Comments

Most likely not.

Answer 1

The base shiny odds for ORAS are 1/4096.

Generation VI slightly changed how Shiny Pokémon are determined to double the default chances that a Pokémon will be Shiny. The basic formula remains the same, but the threshold for a Pokémon to be Shiny is now 16 instead of 8. This results in a base Shiny probability of approximately 16/65536, or 1/4096.

Source

Of course, there's ways to boost these odds. A detailed thread highlighting those methods can be found here.

Answer 2

There is no change to the shiny rate. Here are 2 links.
Link 1
Link 2
Hope this helps!