Made naming directions of predicate methods a bit more specific

I'd like to kindly disagree with the naming choices in: http://batsov.com/articles/2013/09/24/lambdas-slash-procs-in-case-expressions/

I think adding a ? will result in an expectation that the method returns a boolean. However, it returns a lambda, which will be truthy (I guess), which might lead to obscure bugs, or at least suprised faces.