Mine did the same! He hasn't quite turned 7 yet (he will in Feb) but overnight he moved into his own bedroom at night and wants to do all sorts of grown-up things, even his play and talk with his friends has changed and is suddenly more mature.
I remember when I was growing up, every time I moved to a new stage of maturity my dad would act all sad and tell me that I was making *him* old. Which consequently made me feel terribly guilty and made me want to hide my new maturity. It ended up with me sobbing when I got my period because I was definitely going to kill my dad with that.
Which is not what I think you're doing! But it's why I try to greet each new stage wil joy and excitement and tell him how proud I am of his new accomplishments.
ETA: We've got new attitude along with it, too. Every new stage comes with boundary testing, doesn't it?!
I don't accept that new maturity must come with new attitude, though, so every time something ugly comes out of his mouth I remind him that he must speak respectfully and re-state what he said in an acceptable way.
Example...
MOM: DS, get your shoes on, it's time to go.
DS: Fine (in voice dripping with attitude).
MOM: DS, you must speak nicely to me. You can say, "OK, Mom, I'll be there in just a minute!"
DS: Fine (still attitude).
MOM: You mean, Yes, Mom! (and then, move on.)