It's always about Woking with you. This has nothing to do with Ron Dennis and Max Mosley's petty squabble.
And, once again:
McLaren have not said they will leave.
McLaren are involved in the sense that they've been the main team pushing for extra revenue for the teams and threatening a breakaway series for years. The reason it couldn't go ahead was because Ferrari were paid off by Ecclestone, amongst other favours from the powers that be. With McLaren's allies, such as Williams, keeping their heads down, not wanting to get burned, the FIA and Ecclestone were able to give McLaren a hard time. Now Ferrari are onside with the teams, who are now willing to stick their head above the parapet. The FIA and Ecclestone's divide and conquer tactics will no longer work. Unless they want mass insurrection, they'll have to agree terms with FOTA.

Ayrton Senna: WDC 1988,
1989, 1990, 1991
McLaren: WCC 1974, 1984, 1985, 1988, 1989, 1990, 1991, 1998,
1999, 2007McLaren: WDC 1974, 1976, 1984, 1985, 1986, 1988, 1989, 1990, 1991, 1998, 1999, 2008