Would have liked to see the Unicron/Quintessa storyline play out - besides that I have no real regrets seeing this universe end. It had a good run - including the upcoming Bbee one, 6 movies is a respectable amount.

Optimus has come back to life and so has Megatron. Most of the other big name Con's had been used and killed (Starscream, Soundwave, Shockwave, Galvatron (sorta)) so they were going to be struggling to find other big name bad guys who were recognizable to more than just the hardcore fans. Don't think many besides the really committed TF fans would know who Bludgeon or Thunderwing or Overlord are.

I think it came home to me when I got my TF5 Blu Ray in the mail, watched it once then put it away and realized I may never watch it again. Not that I hated it, I just had no real interest.

Plus the toyline hasn't been spectacular in recent years. TF2 had an amazing toyline and there were a lot of good ones from TF3 as well. However the TF4 ones were too simplistic and TF5 - where are all the toys of the characters that were in the film? Instead we get another Slash etc. It's a bit like they forgot how to cash in on a film. And I had no interest in getting yet another Bbee camero or Optimus in his current truck mode (though I do have a TT Nemesis Prime on preorder).

I think a few years break between the Bbee movie and the reboot will be good for the live action franchise, it may result in renewed interest from the general populace.