File this under "grain of salt" but Christian Today (how is that for an odd source for movie rumors?) is reporting that one plot point being considered for Transformers 5 would introduce the movie version of the Quintessons and Ultra Magnus. Optimus Prime would meet the Quintessons, who in the movie-verse would be the Transformers creators, to get answers about why they wanted to kidnap him from Transformers: Age of Extinction. Part of the plot would include introducing Ultra Magnus who would have history with Megatron (now Galvatron).
The Quintessons and Ultra Magnus are both from that 1986 movie. In the movie the Quints were a five faced squid thing that liked to fake at being judge, jury and executioner. Later in season 3 of the original Generation One cartoon they claimed to be the creators of the Transformers with the Autobots being created for labor and the Decepticons for military conquest. Their treatment of their own slave race resulted in rebellion that led to their banishment from Cybertron. This contradicts the other origin (from the Marvel comics) of the Transformers being created by the god Primus who created the race to help him in his fight against Unicron. Suffice it to say the origin of the Transformers has several versions but the one used by commonly for the last 15-20 years is the Primus vs Unicron dynamic in some form or fashion with the Quints essentially being the TF Universe's equivalent to mob bosses. As for Ultra Magnus, he was and remains a stuffy bureaucratic who believes in following rules and regulations to the letter which makes him a not so great leader despite Prime's faith in him.
The general rule of thumb is if the rumor is nearly a straight line to Unicron, it is a red flag of a likely fan generated rumor that somehow got snagged as legitimate by those that don't know better. The classic version of Unicron will never be in the movies. The idea of a transforming planet is literally too large a concept for the live action movies to tackle just for budget reasons alone. There is a reason why the movies remain Earth bound and spends (too) much time focused on human characters. In robot form, the Transformers are the literal definition of "time is money". Relatively speaking, any scene without a Transformer robot in it is millions not being spent on visual effects. It is also why Bay has cheated the transformations (cutting to/from robot mode to just finishing transformation or already in alt mode) because by cutting the full sequence he gets to spend that money elsewhere be it longer robot appearances or larger action sequences.
I could see Ultra Magnus showing up mostly because at this point character names are just picked based on what has cleared any copyright and trademark hurdles and little to do with the character the name represents. There is nothing stopping them from designing a new TF, assigning whatever vehicle they got for free from the car company and then slapping the Magnus name on it keeping in mind they can't go with his classic red-blue color scheme as that is Optimus' and part of the TF design is to assign a specific color to each character so audiences have a quick shorthand to identify each character. Magnus' other color is white so around this time next year see a mostly white vehicle on set.... As for the Quints, the only reason I can't just 100% dismiss this is Hasbro will have zero legal problems with their names so they are clear to be used to ID whatever alien race is designed for Prime's search for his creators and oddly there are not that many alien races in Transformers 25 year history so by default they become a natural choice for a name. Just don't leap to the conclusion that they in turn will lead to Unicron.