do you think the characters of mlp will change in 2012? meaning,will they grow older or something?

Yes They will

I think they'll still be the same since they didn't change in 2011.

I think they do change! Each time a pony learns a lesson, she seems to improve something about herself.
But, if you mean getting taller, voice changes, moving on in life, etc... Then no. I think they'll stay the same.