But that's not according to the latest media speculation, which is mentioning Force India's Paul di Resta and former McLaren driver Heikki Kovalainen as potential candidates to replace the 2008 world champion and Monza winner.
Plan A, however, is undoubtedly re-signing Hamilton.
"I can imagine we'll have some conversations before Singapore," team boss Whitmarsh said.
But he also admitted it is not too late to slot in a new driver alongside Jenson Button for 2013, and also played down the knowledge about McLaren's next car that Hamilton might take to a rival team.
"Developing next year's car is the work of technologists, engineers and designers," Whitmarsh insisted.
"The drivers, apart from when they sit in it, are not that intimately involved in the process."
Publicly, Whitmarsh is not worried about the situation, describing Eddie Jordan's claims that Hamilton is definitely switching to Mercedes to replace Michael Schumacher as "fantasy".
Under the surface, though, the situation inside McLaren has changed. One hint is that Button is now point-blank refusing to fall in line behind Hamilton by obeying any 'team orders'.
"I'm not going to go out and pedal round and sit behind my teammate," he said.
"At the moment, the dynamics are right within the team and it will be some time before we change our approach," he said.
Should Hamilton leave, Scot di Resta looks the favourite to replace him. He would ensure McLaren keeps its 'all-British' lineup, and his career is already handled by Button's manager Richard Goddard.
Asked if McLaren has targeted di Resta as a potential driver, Button told the Telegraph: "That is not for me to say, that is for his management to say."
The Daily Mail has mentioned 2008 and 2009 McLaren driver Kovalainen as another candidate, while the wilder rumour-mongers have named another Finn.
But Finnish commentator for MTV3, Oskari Saari, thinks the speculation about Williams' reserve driver Valtteri Bottas is wide of the mark.
On the other hand, "Williams knows that if they do not take Valtteri (in 2013), there will be takers for him from other teams", he warned.