The Bee movie *is* TF6. Even if it's not a sequel/prequel, it's still the 6th TF movie. Hell, one of the reasons most franchises have abandoned numebred sequels is it makes it easier to reboot/retool/prequel/sidequel/spinoff. And it also makes movies seem more accessible if they're not numbered. People see "Transformers 7" and think they've gotta watch the other six. Dropping the number means people just casually paying attention have less clue as to how many came before (which in some franchises helps because the continuity is whack anyway).