China's economy is in "long-term decline" and growth from 2020 will be increasingly dependent on foreign capital

This year, the current account shortfall could be 0.3 percent of its GDP, and slip further to 0.6 percent in 2020, the bank predicted.

The report blamed the shrinking current account on China's aging population, and flattening market share in goods exports, among other factors. But there are opportunities for investors too, the bank said.