Currently w.wm_attributes() without arguments returns a tuple or a str, which is inconvenient and different from other similar methods. I propose a change that makes it returning a dict. No deprecation period is possible. For details see:

https://discuss.python.org/t/tkinter-wm-attributes-needs-breaking-changes/37360
python/cpython#43457
python/cpython#111404

I think that this change should be made 16 years ago.