As long as she's healthy and motivated, I can't see why she couldn't play for more than 2 years. Age is just a number. Plus she didn't play much tennis as the others during the younger age. So she can still play until 35.
She is really capable to play for another 2-5 years, depend on how she is motivated. I cant see her physical condition slip away. She just to the mentality and extra belief. I think she can reach more than 1 slam final before she retired. And end top-10 in every year from now on (i mean since 2011)
Asian Tennis Legend - Li Na
Wozniacki Kvitova Pironkova