If the object is constructed in the scope of the const member fn invocation, and if all the non-const member function invocations between the object's construction and the const member fn invocation are statically bound, and if every one of these invocations is also 'inline'd, and if the ctor itself is 'inline', and if any member fns the ctor calls are inline, then the answer is 'Yes, the soon-to-be-standard interpretation of the language would prohibit a very smart compiler from detecting the above scenario, and the register cache would be unnecessarily flushed'. The reader should judge whether the above scenario is common enough to warrant a language change which would break existing code.
