Strictly speaking f6 isn't a toggle
It will cycle through all open panes not just those two and if you don't have the results pane visible it won't show it.
You could argue that ctrl-R would better fit as an answer as that is a toggle and will show/hide the results pane.
Yes. The way I have SSMS set up that means that (assuming I have run a query since opening SSMS and that no other query panes are open) by default it will circulate query-results-messages