Bill Gates (left) and Warren Buffett visit the battery examination center of BYD Auto in Huizhou,Guangdong province, on Tuesday.

Amid the weeks-long buzz created by the visit of US billionaire philanthropists Bill Gates and Warren Buffett, the most pressing question is: Guess who's coming to dinner on Wednesday evening?

Beijing Chateau Laffitte Hotel, a European-style lodging house in the north suburbs of the city, is reported to be hosting the Chinese and American super-rich guests starting at 5 pm.

Details of the "private gathering" between the Chinese rich and two of the richest Americans remained mostly secret. The attendees are still unknown.

The banquet - dubbed by local media as the Hongmen Banquet, a historical anecdote indicating a feast or meeting set up as a trap for the invited - has ignited a fierce debate on the merits and difficulty of philanthropy and charity for the country's newly wealthy.

Only a few of the 50 Chinese billionaires on the invitation list have publicly answered the call, with names including "China's No 1 philanthropist" Chen Guangbiao, CEO of Jiangsu Huangpu Recycling Resources Co Ltd, who is worth an estimated $440 million according to last year's Hurun rich list.