Howard Schultz (pictured), Starbucks CEO, has resigned from the board of Square to be replaced by former Goldman Sachs CFO David Viniar, a move which will likely kick off speculation the mobile payments firm is plotting an IPO.

Schultz joined Square’s board 14 months ago, following an alliance struck in August 2012 between Starbucks and the payments startup.

The coffee chain joined a funding round for Square and handed over the processing of credit and debit cards, as part of the link-up. Consumers can also pay via Square in Starbucks outlets.

Both companies claimed it was always Schultz’s idea to serve on Square’s board for one year only.

Viniar is retired from Goldmans but is well respected in financial markets — just the kind of profile Square might need if they are manoeuvring towards an offering. At least that is likely to be the speculation moving forward.