The guy is just so effective and well conditioned to be going anywhere anytime soon. I'm of the opinion that he'll be effective in the NHL until he's around 43 years old. After that he'll probably tail off a bit and maybe go back home to play for Bratislava in the KHL.
IMO, he'll finish his career as a top 10 defenseman of all time. Possibly even into the top 3-5.
He's known to be a health freak (does not drink, etc.) and has an unbelievable training regimen. I am taking the over and think he'll remain until he's 45; big drop-off after 40, but still an NHL player.
I'm not taking anything away from Lidstrom or Chelios, they worked hard until the end.
But I have to imagine its just a little easier finishing off your years as a top pairing, or second pairing, shut down defenseman if there is less asked of you.
If you are being relied on to run the PP still, and play physical, and 1st line minutes, then you aren't going to last. little aspects of your game will diminish slightly, you will overexert yourself.
If a team is a competetive team, and there is a talented defensive group around you, and you just have to fill in a role without carrying the team like you maybe did at 30, then you can last longer. If you are brought in to a bottom feeder team and asked to be a big part of their first attempt to make the playoffs in 5 years... then not so good for your future.
For example, I think 3 years if he played on a bottom dwelling team and 6 years on a playoff/cup contending team.
Chara's best season of career came last year at 35.
I think his numbers will start to come down as he slowly starts to give up PP minutes tp younger more fleet of foot defenseman like Hamilton and Krug. He's in great shape, but managing his minutes is going to be important. In 2-3 years he'll be an ES and PK defenseman exclusively IMO. His value comes in his shutdown ability.
He is under contract until 2017-2018. He's a freak but I can't see him playing after his last contract year. He can play at a high level for another 3 seasons in my opinion, barring unforeseen circumstances.