...they feel the lower than expected toy sales for Transformers DOTM were due to the recurring cast of robots in the previous trilogy. They hope new Transformers characters will reignite toys sales...
It has more to do with making over 9000 different versions of Optimuses and Bumblebees while neglecting requested figures like LeaderClass DOTM Megs, Dino and cancelling that Voyager Jetwing Prime that actually looks cool. And stupid designs like Que, Wheelie and Brains.
Seriously. I know I saw three different versions of Bumblebee, but toys like Skywarp, Que, or Soundwave you had to import, if they bothered to make a toy at all.
What's the point of making the movie if you're not going to make toys of the characters available.