The speculation is being fuelled by news that the start-up's managing director and third founding partner will be Mark Wilson who, until the end of last year, ran the £9 million Waitrose account at Banks Hoggins O'Shea/FCB.
The three insist they will be starting with a blank client list and declined to comment on the prospect of Waitrose's imminent arrival. All are currently subject to a restriction preventing them from going after BHO business.
Unusually for a start-up, however, the partners have confirmed they are looking to recruit up to a dozen creative, account and production staff.
They also plan to add an as-yet-unnamed fourth partner.
The fledgling operation, to be called HOW, will operate from the London office of Miles Calcraft Briginshaw Duffy, which will be taking a minority stake in it. The deal will also allow HOW to use MCBD's back-up services.
A Waitrose spokesman this week ruled out plans for an imminent review out of BHO. "We have been aware of the speculation about what Ken and Chris might do and we continue to take an interest in what former BHO employees are up to but we continue to work with BHO just as we always have done," he said.
However, industry sources claim the business will be reviewed out of BHO by next month and the start-up would be the favourite to capture it.
HOW's success might present a conflict problem, however. MCBD already handles the rival Kwik Save chain's creative account.
Hoggins, 54, and O'Shea, 55, who left BHO at the end of December, said they had been discussing plans to go it alone for more than a year, having grown increasingly disillusioned with life as part of a global network.
"We feel there's a more civilised way of doing things," Hoggins said.
"The FCB deal changed things and it became frustrating," O'Shea added.
The pair, the one-time joint executive creative directors at Lowe, admitted they had discussed joining MCBD but wanted to be free to make their own decisions.
Jeremy Miles, the MCBD chairman, said: "It's always good to invest in talented people. We've known Ken and Chris for many years and we believe they are more than capable of building a very good portfolio of accounts."