China's economy will likely grow at 6.1% this year, and it won't drop below 6% in 2020, according to a former central bank adviser.

"Whether China will maintain 6% growth is not a valid question anymore," Sheng Songcheng, a former director of the People's Bank of China's statistics and analysis department, wrote. "The Chinese economy has bottomed out."

Consumption, investment and trade are expected to recover, and the economy has shown signs of marginal improvement, according to Sheng. "The current reform measures and technological advancement should create huge growth potential for the Chinese economy," he said.

Sheng's comments are surprisingly upbeat, even taking into account the pick up in economic data in November. Other economists remain skeptical of the sustainability of the rebound, arguing that the data may have been boosted by delayed production or policy distortions, rather than real demand.