After moving his way up through the Football League with prolific spells at Swindon Town and then Burnley, Austin moved to QPR in 2013.
His 19 Championship goals fired the club to promotion via the play-offs as QPR bounced back at the first attempt following relegation from the top flight.
Austin has looked comfortable in his new surroundings, netting 11 league goals in 15 appearances to spark speculation about a possible England call-up.
In a press conference on Wednesday, ahead of the Boxing Day trip to Arsenal, Redknapp said the striker's future would potentially hinge on whether QPR retain their Premier League status.
"He's got 18 months left, Charlie," he said. "He's not going anywhere in January so it's up to Charlie and everybody else.
"We'd like to keep him here long-term but we've got to stay in the division. He's proved he's a Premier League player and he wants to stay in the Premier League."
Asked if he felt Austin was likely to move, Redknapp replied: "Not at the moment, not in January. Once he's into the last year of his contract it's a different proposition.
"But we've just got to focus on this season. Everybody needs to do their job, Charlie needs to keep scoring goals and if we do that then I'm sure we can secure his future at QPR.
"Charlie is playing and scoring goals in a team that hasn't made a million chances.
"When the chances comes along he takes them so that's even more credit to him for what he's done.
"If he was playing at someone like Chelsea or Man City he'd probably have even more."
