They are crying, that's for sure. Why they are choosing to do so with seeming regularity is the big question. Genuine concern? CYA? Do they feel that keeping a little fear simmering is to their advantage? Do they feel that such warnings will make any terrorist think twice about attempting an attack because "we're all ready and watching because we were warned, so there is no chance of success?" Could be any, or a combination of all, or none of these for all we know.
As to the prospect of another attack, you nor I nor any other American wants it to happen. But if the CIAs statement is to be believed, we are guarenteed another one. So, what do we do with this knowledge as individuals? At this point about all we can do is hope for the best but expect the worst. And IMHO, until we decide to make some dramatic changes in a few areas, most notably our borders and immigration, expecting the worst won't be time spent worrying over nothing.