Talking to Demonac last night on Messenger, I was able to work out that in the Dlx class, we've had 6 of the 200x Camaro car - 4 of which are virtually identical in vehicle mode (1 is the DotM W3 Nitro mould & 1 is the DotM W1&4 'stockcar' mould - both of which weren't even in the movie in that form).
The main thing differentiating those 4 "identical" Dlx Bees is the gimmick. Not noticing the gimmick, or caring about a gimmick... aside from dedicated collectors who buy multiples of characters - who's gonna buy more than one of what ends up looking like "the same toy"?
Hasbro should have been investing that time & money (of the last 5 Dlx Bee moulds) into toys of movie characters that don't have a toy, or characters that "need" a toy in certain other size classes.
Re-releasing the same mould may draw criticism from some vocal fans, but most fans won't buy yet another Bee anyway... and of the ones that do if it is a new mould or gimmick, is an insignificant amount of sales to Hasbro - so why waste the time & money.

I'd much rather see a Mirage/Dino toy released in the first waves than another Bumblebee... and it would sell a lot better to fans & non-fans alike (red sports car that featured in the movie - an instant hit on the pegs full of black, grey & yellow TFs).