Lampard, 34, and Cole, 31, have both failed to agree extensions to their current Stamford Bridge contracts.
Benitez, who replaced Roberto Di Matteo as Chelsea boss this week, admitted the pair could leave the club next summer.
Asked if he thought they would be moving on, Benitez said: “I think so. I think that’s the case at the moment.”
He added: “I don’t have all the information, but it’s not fair to tell me I’m only here for seven months and then expect me to have an influence at the club over the next two or three years.”
Lampard, who has played for England 93 times, joined Chelsea from West Ham in 2001 and has gone on to become the club’s third all-time leading goalscorer with 189 goals from 571 games.
Cole, capped 99 times by England, has also won a Premier League title, the FA Cup four times and the Champions League since joining Chelsea from Arsenal in August 2006.
It could be the second successive summer where Chelsea have lost two of their key players on free transfers after strikers Didier Drogba and Salomon Kalou left Stamford Bridge earlier this year after failing to agree new contracts.