While the move is undoubtedly a step in the right direction, however, the Rs would be wise to still look out for another forward this summer.
Sigthorsson is 24 and could form a deadly partnership alongside 25-year-old Charlie Austin, who has been tipped to thrive in the Premier League next season.
The two of them alone, though, will need support from elsewhere.
Bobby Zamora is still yet to sign a new deal with the club, while Loic Remy has been heavily linked with a move away from Loftus Road.
Were Remy to stay in west London, of course, that would likely be problem solved. But, with the Frenchman's current situation, you can understand Redknapp searching the market for new strikers.
Gary Hooper and Jermain Defoe have previously been linked with the Rs and one of the two, or an alternative option, should do the job.
During a grueling Premier League campaign, Austin and Sigthorsson can partner up or play as lone strikers, though the possibility of injury or suspension deem another forward necessary.
The Iceland international, meanwhile, is not guaranteed to adapt to the Premier league straightaway. Luuk de Jong and Andreas Cornelius are just two examples of strikers who have failed to meet English football's tough physical demands.
Renewing Zamora's contract, then, would be step one, with a new signing step two. QPR scored just 60 goals in 46 Championship games last season - and depth up front will be the key to ensuring Redknapp's side fare far better in the final third next term.