"But I have a year on my contract left at Preston and we will have to see what happens."
Northampton Town meanwhile have told Forest that goalkeeper Mark Bunn would cost them in excess of £1m.
"We've had about six bids from Forest before for Mark," said Cobblers chairman David Cardoza.
"He is a terrific player and we have a certain value for him which will break the club record."
Possibly leaving the City Ground is defender Matt Lockwood although Orient have denied he will be returning to East London.
"If I'm honest I would say there is absolutely no chance that Matt will be coming back to us this summer," O's boss Martin Ling told the Leyton Guardian.