No matter what the fan community says, these films are very well liked by the general public, expecially Teens, since it pretty much delivers in what they like to see more in movies, getting kick-ass special effects and action, as well as American Pie type of comedy.
I like these films on a purelly visceral level and due to that am quite hyped for Age of Extinction. They're not great films, they're actually kind of bad, but i still find them incredibly entertaining, i also like to see one of the few last classic type of film franchises, as you don't get constant promises for "the next film" with stingers and they don't give you half a movie because of an already planed sequel, each film earns its sequel.
As for a reboot, no matter how bad Bay's era was, it will get a major stygma unless it offers a fresh new experience like the recent Godzilla reboot. And then, most of the public of these films may end up being disapointed in seeing a Transformers film with not as incredible special effects or with less focus on the military.
When the inevitable reboot transitating from Michael Bay to a new Director comes out, i see a similar situation to Spider-Man happening, where a high priority franchise close to getting the top 1 of the box-office suddenly loses much of its steam and has to win its audience back.