O'Driscoll and D'Arcy missed Ireland's second match of the championship against Scotland at Murrayfield due to hamstring injuries picked up in the opening-weekend victory over Italy in Rome.
O'Sullivan said: "I don't see any reason why Brian and Gordon won't be fit.
They have a lot of hard work to do in the next two weeks and they will be working harder injured than if they were fit.
"That is going to be a very physical match but the boys are going back to Lansdowne Road, which has been a good hunting ground for us.
"It is going to be a phenomenal atmosphere and we are looking forward to the England game."