This idea got sparked in a different thread, and I hope we don't have a similar one so far.
This isn't just about how you wish John to be in S4 (as we already have a thread for that), but how you think John has evolved as a character throughout the show so far (and how you think, or hope, he will evolve in the future).
Personally, I see John's evolvment a bit like this:
He started out as depressed and lonely man in the beginnig of ASiP, a man without meaning or purpose. He meets Sherlock, who gives him a sense of direction and interest again. However, throughout S1 he has the slight feel of an "underdog". Sherlock is rude and John hasn't quite learned how to deal with him yet.
In S2, we see a much more balanced John. IMO, we see John at his very best in HoB. He shines in this episode. He has learned to deal with Sherlock being Sherlock, they are both on equal footing, John is secure in himself, who he is and his friendship with Sherlock.
This starts the slow decline from TRF. Mostly because of the strain of what's going on, and of course, the loss of Sherlock. That doesn't just mean the loss of his best friend, but the loss of purpose and a way of life.
In S3, we never see John back at the top of his game anymore. He's more angry, tense and frustrated. Mostly because of outwards circumstances that he has to deal with hitting him more or less constantly - Sherlock returning, getting married, almost losing an old friend (Sholto), Sherlock starting drugs again, John not being content with his newly-wed life, becoming "a bit smoked", his wife turning out to be an assassin, Sherlock being shot and almost dying from said wife, Sherlock killing a man in cold blood, Sherlock being sent away for good (they think).
That is a lot to handle for a guy who already has issues with expressing his emotions. He doesn't have the time to deal with one issue before he gets hit over the head with another one. This all leads to him becoming angry, snappy and short-tempered, more so than in any other seasons.
For future series, I would hope that he get a chance to breathe and calm down, so that he can find the equilibrium he had in HoB. However, from what I understand from Mofftiss, that is not to be. So it will be very interesting to see where John will go in the future.
I will end this (rather long) start post by saying that outside of HoB, my favorite John is found the pilot. It's a subtle difference from ASiP in the series, but in the pilot John is a bit more pro-active. His smiles are broader, bit more active (taking notes) and a bit more direct and outgoing towards Sherlock. (I absolutely LOVE the restaurant scene with John going "Because we are idiots" with his not-looking-away stare and delibarate chewing).
To me, Pilot!John is the John I read about in fanfics. I wish they would've kept him in the series, although we see him a bit more in HoB.