Foreign investors' purchases of Chinese bonds will probably surge more than fourfold in the coming two years as global central banks diversify their reserves.

Monetary authorities and supranational organizations will lead buying of about $48 billion in 2017 and 2018, according to a Bloomberg News survey of 11 analysts. That's more than four times the $12 billion of the whole of last year. Inflows have slowed to $8 billion so far in 2016 as the yuan's 4.2 percent decline sapped investor confidence.

"There's still huge potential for reserve managers to diversify slowly their reserves into the yuan," said Paul Mackel, head of emerging-markets currency research at HSBC Holdings Plc. "The appetite from real money managers, such as pension funds and mutual funds, is again very, very high. If China is eventually included in major bond indexes, it could bring an average $80 billion-$100 billion annually over the coming years."