As I begin to consider the implications of ANY sort of disciplinarity (name your favorite), I find myself always circling back to considerations of ultimate outcome, i.e., what are the needs in terms of how citizens/colleagues/activists/designers/etc. operate now and in the future? If we decide that designers should operate along fairly narrow lines of problem-solving, then it stands to reason that the very notion of a discipline will, and should, be informed by that operational imperative. As such, the conversatio0n about various ideas of the design discipline will obviously relate a great deal to considerations of the profession.
To stake out my limb and take a step on it, I would offer that the most common educational approaches at this point are increasingly unable to bridge the gaps between the narrow "a to b" problems of the past and the incredibly complex (and complicated) challenges that designers are now dealing with in the professional arena.
Is professional design practice (and therefore education) interested in realtively formulaic problem-solving (styling?) versus decision makers and problem solvers that work carefully and widely through the murky issues that true solutions entail? Some call this "high value" thinking while others call it "big mindedness" (Roger Martin at the University of Toronto uses these phrases and refers to the need in business education for such thinkers, integrative people who can balance "multiple and possibly conflicting models...").
I would suggest that the very questions that are being asked of business education strike right at the heart of our discussion...