Extend jQuery with enable/disable function
Overall it looks quite nice.
Just a few points:

The parameter name is asking a question about the element, not making a statement of what to do. I would rename it to disable which enables the caller to better signify their intent.
In the same vein, I would also rename the function to ariaDisable as it performs an action as opposed to asking a question

Edit
Per m90's comment the loop is per jQuery plugin conventions as noted here