I think he'd agree with you from what he's said in interviews. When a Dark Tower idea comes to him, I have no doubt he'll write that story.I'd say there's always room for another Roland tale, something from the period between the fall of Gilead and his pursuit of the Man in Black. I know the comics tried covering this period, but those are comics, written by others, mere pastiche--hardly the real deal. Reading DT, I've always felt there are countless unknown adventures in Roland's past--countless untold tales.
Just sayin it wouldn't break my heart to hear he's writing another.