Proposed resolution (August, 2011):

Change 13.2 [temp.param] paragraph 11 as follows:

...A template parameter pack of a function template shall not be followed by another template parameter unless that template parameter can be deduced from the parameter-type-list of the function template or has a default argument (13.10.3 [temp.deduct]). [Example:

  template<class T1 = int, class T2> class B;   // error

  // U cannot be deduced from the parameter-type-list or specified
  template<class... T, class... U> void f() { } // error
  template<class... T, class U> void g() { }    // error

—end example]