The reopening of Chinese stock markets on Friday after a week-long hiatus will give them their first litmus test. Share prices are set to show whether the disappearance of the former "bagman" to families of Communist party leaders forces his powerful backers to liquidate their holdings. Others are speculating on a renationalisation of assets held by Mr Xiao or his Tomorrow Group.
The 45-year-old financier has not appeared in public since he left his Hong Kong residence in the early hours last Friday, accompanied by Chinese security agents. He later told his family he was in mainland China, according to people familiar with the investigation.
Mr Xiao liked to style himself a value investor and disciple of Warren Buffett. But his primary asset seemed to be an ability to make himself useful when China's powerful families needed to move money around. Shell companies he controlled were instrumental in several deals involving families of Chinese leaders. These include the 2006 privatisation of Luneng Group, a state-owned power company in Shandong that was later renationalised, and the 2013 sale of a stake in Ping An Insurance.
In recent days the previously censored 2006 story of the Luneng privatisation by the family of Zeng Qinghong, a politician allied with Jiang Zemin, the former president, has been allowed to circulate freely on social media in China. Its resurrection is seen as a sign of larger political motives behind his repatriation.
His known investments stretched from chemical plants and coal mines near his wife's hometown in Inner Mongolia to property ventures and Ping An.
"He controlled a lot of companies so if his disappearance is proven it will certainly affect some of the shareholdings," said Hong Hao, head of research at Bocom International in Hong Kong. "People want to know if there will be any change in the ultimate ownership of these companies."
Chinese media reported in 2013 that Mr Xiao controlled nine listed companies and 17 banks, and that he held investments in a total of more than 30 financial institutions. Other estimates reach as high as 60. One 2013 commentary published on the website of the state-controlled People's Daily referred to Mr Xiao as a "porter" rather than creator of wealth.
The Hurun report, a Chinese rich list, put his net worth in 2016 at $6bn, making him the 32nd richest person in China, after he talked them down from a higher ranking.
Richard Hoogewerf, chairman of the Hurun Report, told the Financial Times this week it was extremely difficult to work out Mr Xiao's wealth because "he's a got a myriad of highly complex structures". His full holdings are not known and many of his investments are thought to be through unlisted holding companies.
On Wednesday, after the Financial Times reported Mr Xiao had been taken from the Four Seasons, a luxury hotel and apartment block in Hong Kong, Tomorrow Group took out a front page ad in Hong Kong's Ming Pao newspaper "clarifying" Mr Xiao's whereabouts and repeating messages from the company's social media account that had been censored the day before.
Half pleading, half defiant, the company claimed Mr Xiao was "receiving medical treatment overseas" and denied he had "harmed the interests of the country" or "supported any opposition organisation". It added that he was a Canadian citizen enjoying consular protection, as well as the legal rights of a Hong Kong permanent resident.
Tomorrow Holding's website has been inaccessible since its founder disappeared but the company said in a social media message late on Thursday that its operations, as well as those of its subsidiaries, remain normal.
At its low-rise yellow building on a leafy street in Beijing's technology district, there were no signs indicating its presence, nor that of the two technology companies that moved into the third floor a few years ago. Most offices in China are closed for the final day of the new year's holiday on Thursday, so no employees were in sight.