In the wake of the 'Multi-21' team orders affair, Red Bull denied speculation Webber's role as teammate to world champion Sebastian Vettel is now untenable.
But even billionaire Mateschitz, a known strong supporter of 36-year-old Webber, agrees that the Australian could leave at the end of his 2013 contract.
"Whether he retires, only he will choose," Austrian Mateschitz told Speed Week.
"(But) Mark is definitely a candidate for 2014.
"He is always welcome with us. So too would be a quick junior like Vergne or Ricciardo from the Toro Rosso team," he added.
"Sorry, I know it's a diplomatic answer which leaves everything open, but that's how it is. Everything else is pure speculation."
Fascinatingly, Mateschitz also mentioned Finn Raikkonen - a close friend of Vettel's - as also potentially in the running for a 2014 seat.
Often mentioning the 2007 world champion in interviews, Mateschitz is an open admirer of Raikkonen's, having sponsored the 33-year-old's two year rallying foray in 2010 and 2011.
Contradicting April Fool rumours that Raikkonen has announced his impending retirement, Mateschitz said: "Kimi is cool and fast and always a candidate."
Germany's Bild newspaper reported that Webber has "already been in contact" with Porsche officials, regarding a new 2014 prototype team for the famous marque at Le Mans.