Also, Aang doesn't count either because once an Avatar dies, another Avatar is reborn so it is obvious that he dies. It is unknown if the others are dead though.
So far in LOK we've seen Katara, Zuko, Iroh and Zhao.

I would love to see Azula too. It would be really interesting to see what will happen to her. But mostly, I would love to see Toph. I would love to see what she thinks of Republic City today and mostly, what she thinks of Lin and Su Yin.

Definitely.

He would be a funny old man.

Of course!

Definitely! Ty Lee better not come into TLOK, she'll ruin it!

I'd like to see Suki and Sokka as a cute old couple.

Absolutely

Sokka's dead so it's impossible , Toph is alive however (or supposedly) Suki would also be cool to see and Ty Lee too

^Actually, it was never officially confirmed that he died.

Katara says in the first episode "My brother and many of my friends are gone" so it's pretty much been confirmed since the beginning that he's dead.

I forgot about that! Sorry, my bad. I don't really remember the first LOK episode.

I would love to see her.