No. A 7 player game where two players are killed still uses the 7 player rules, just as you don't change the board when someone gets offed.
Note that in the equivalent situation for a 5 player game there would actually only be THREE players left -- that's a part of the reason that I see (though not the only reason) why this rule is important for 5 player games, as the game would completely break down with 3 player left if you couldn't nominate 2 of them.
This has been changed in the final rules.
The number of players evolves with executed players being removed from the count.