Gilead doesn't have 11 billion to poney up. They are still in the hole for the Pharmasset acquisition with a huge debt and only a billion or two working capital. Sofosbuvir is heading for approval in 2014 so it will not be bringing in multi billions until 2014/2015
If gilead would make a deal for Ariad, it would be either stock or some type of more complicated merger which might include making Berger CEO. It's hard to see how an Ariad/Gilead deal would be structured even though it is real easy to hope it happens