QPR boss Neil Warnock hopes to buy a new striker and defender next month.
Johnson's current contract expires next summer and he has been discussing a new deal at Craven Cottage.
A number of defenders have also been identified as possible signings, but players in other positions may arrive on loan.
Warnock said: "If I can get one or two targets I want, then yes we'll pay money. But other than that, I'm looking at the loan market."