He’ll definitely be dead since there is a new Avatar who has already had time to grow up and master three of the four elements.
Fett101 is correct. Seeing as there is a new Avatar, Aang has no other choice but to be dead.
Even if this new Avatar wasn’t grown up already and a master of three elements, Aang would still have to be dead.
That is how the Avatar cycle works. There can only ever be on Avatar at a time, and once that Avatar dies, a new Avatar is born into the next tribe - Fire, Air, Water, Earth. Thus, the Avatar cycle.
After Avatar Roku (Fire Nation) died, Aang was born of the Air Nomads and he was the new Avatar, immediately at birth. Then when he was stuck in the iceberg for 100 years, no new Avatar appeared because he never actually died. Presumably, when Aang dies, Korra will be born into the Water Tibe as the Avatar immediately.
To address your hope Bryoko614, we are more than likely going to see Aang several times in the new series. He should be there to mentor Korra and teach her the ways of being the Avatar, just as Roku appeared to guide Aang. Actually, seeing as Korra is already master of three elements, I bet Aang has already appeared to her several times.
I think it is fitting that the last element Korra must learn to master is air. Such a good way to honor the legacy of Aang and the original series!
Yeah, that’s what I meant about the whole ‘Aang not being alive’ thing. If there’s a new Avatar he has to be dead- there can’t be two Avatars at once. Although by my calculations that must mean he died fairly young…around 67-ish probably. I mean, c’mon King Bumi was 112! I guess being frozen in that iceberg for 100 years messed with his lifeline a little more than it appeared to.
Also about Uncle Iroh…I’m also extremely sad that he’s most likely dead. He was one incredibly awesome old man. R.I.P Iroh. 
Found this online and just thought it worth posting. 
Some new info about the series.
ugo.com/tv/comic-con-2010-le … -interview
As mentioned , the cabbage merchant will not appear, but “his legacy will be present in some form.”
As an evolution of the first series, The Legend of Korra will have more sophistication to it, but still keep the humor, fun hybrid animals, and action.
It won’t cover more mature subject material necessarily, just different mature subjects. “It won’t be another war, but a different sort of conflict.”
On whether or not we’d see a love interest for Korra: “We love that stuff. We’re total cornballs, we love cheesy teen romance. Rest assured, there’s plenty of romance happening in the story, but it’s the same balance of ingredients that we like.”
Katara IS in fact the mother of Aang’s offspring, who will be central to the show. “We didn’t mean for it to be a big super-secret, that they end up together.”
On the persecution of Airbenders being compared to the X-Men registration act: “We’ll see something like that, but in sort of a different structure.”
Will it be a very different world from where we left off? “Yes and no, the world has definitely changed, and evolved, and advanced, but we’re very conscious of keeping the same feeling. Not totally different, but it’s definitely generations later.”
“There will definitely only be one Avatar at a time, and it is Korra.”
So will Aang have any kind of presence? “Yes…in his way.”
DiMartino and Konietzko will continue to work with Joaquim Dos Santos and Ryuki Hung, working to improve the design and animation.
The Legend of Korra will in fact be a mini-series, with Michael and Bryan directly writing each episode.
“As a mini-series, it’s going to be really tight. While we really love the filler episodes, those are some of our favorites, this thing is just lean and mean. It’s a really cool driving story.”
I love Avatar, though I’m not into anime at all. Avatar was just awesome in every way, but I’ll miss the old characters in the new series. I like that the Avatar is a girl though! 
Sounds amazing! I can’t wait until it comes out, I’ll be hooked. I just hope that it’ll compare with The Last Airbender. There were so many plots and characters and the world was massive. I think it’'ll be good though. At least, I hope 