According to Autosport, both team principals Ron Dennis and Eric Boullier are focused on signing Sebastian Vettel and/or Fernando Alonso, who have between them taken six of the past nine world championships (the other three belonging to Kimi Raikkonen, Lewis Hamilton and Jenson Button, all of whom have driven for McLaren) and are prepared not only to pay handsomely, but also to wait: Vettel is currently signed with Red Bull through the end of 2015, and Alonso with Ferrari through 2016. But both have struggled this season with cars that can't keep up with the front-running Mercedes, and could welcome the opportunity to start afresh with a new team – and a highly successful one at that.
Of course, McLaren hasn't been at the top of its game lately either, but the Woking outfit is at the dawn of a new era. Next year it's bringing Honda back to the grid with an all-new engine that may take some time to break in but stands a chance of threatening the Mercedes' dominance this season in a way that the Renault and Ferrari engines have not. It just needs the right drivers to pilot them.
As of yet, it seems that McLaren has not received a firm "no" from either driver's camp, and appear to be eager to continue pursuing either or both until they're told otherwise. In the meantime, the team is leaving its current drivers Jenson Button and Kevin Magnussen in limbo with the prospect of being signed for another year, another few or not at all. It all depends on what becomes of Alonso and Vettel.
After winning his back-to-back titles with Renault, Alonso briefly drove for McLaren in 2007. That was the same in which Vettel made his race debut for Toro Rosso, two years before switching to the Red Bull team he's been ever since.