"Two years for probably both of them actually I think," the Red Bull driver, who is departing F1 for Le Mans sports car racing with Porsche at the end of the year, told the British broadcaster Sky.
"And then what they (Ferrari) do after that obviously (is) pick Seb up off the back of Red Bull and then they keep moving from there."
'Seb', of course, is Sebastian Vettel, Webber's teammate of the past years who - in an identical Red Bull - won three and now almost four world titles compared to Webber's 9 grand prix wins.
But the 37-year-old backed Ferrari's next pairing, saying Alonso and Raikkonen is "a very short-term aggressive statement from Ferrari to put the team at the front".
Webber thinks the move is justified on the basis that Alonso needs "to be pushed".
"He needs to be squeezed on Saturday afternoon to get the car further up the grid," he added.