German newspaper Bild report that Webber is top of Porsche's list to drive their LMP1 car in the 2014 24 Le Mans and the eight race FIA World Endurance Championship. Bild say Nick Heidfeld has already been recruited by Porsche and has been enlisted to smooth-talk Webber into signing for the team. The two drivers were teammates at Williams in 2005.
Porsche have built up a 170 strong workforce, based in Stuttgart, who are working on the Le Mans racer.
Signing Mark Webber and Nick Heidfeld for 2014 will be a massive statement of intent for Porsche who are still clinging on to their record 16 wins at Le Mans (Audi have won 11 times).
If Webber decides to leave Red Bull (or is pushed out) Mateschitz is already lining up Webber's replacement for 2014. He recently said of Kimi Raikkonen - "Kimi is cool and fast and always a candidate."
Mark Webber has history in sports car racing, having driven for Mercedes AMG in 1998 and 1999 where he won 5 out of 10 races in the FIA GT Championship. At Le Mans 1998 the Mercedes retired with mechanical issues and in 1999 the car famously flipped at Indianapolis and the team withdrew.
If you're not convinced by all this have a watch of Mark talking about his own Porsche 911 GT2 RS here.
Update - several sources have claimed this rumour as fact and that Mark will drive for Porsche on a 5 year contract.