"Dragon Ball Super" is scheduled to begin its new arc on December 18, with the story focusing on Hit trying to assassinate Son Goku upon the orders of an unknown individual. The unknown individual could be anyone currently in the series, or some new enemy, but two individuals who could have ordered that is Beerus and Whis.
According to Otakukart, anyone from any of the 12 Universes in "Dragon Ball Super" could have ordered Hit to assassinate Son Goku. It's also going to be hard to predict it, especially if it's going to be a new character.
But it's not a new character, it's actually Beerus and Whis that ordered Hit to kill Son Goku, not because they want him dead, but because it's part of his training to become stronger. But why would Beerus want Goku to be stronger?
One reason if for the upcoming 12 Universe Tournament that the Omni King Zenos is organizing. Beerus would want nothing for his team to win, and a stronger Goku increases the chances of his team winning.
Another reason is that Beerus just wants Goku to become stronger as he is always looking for someone to challenge him. Reddit user Danbito mentions in a post that Beerus allowed Goku and Vegeta to train with Whis because he wants both of them to entertain him or give him a worthy battle. He constantly refers to the Saiyans as his playthings in "Dragon Ball Super".
But is it possible that other characters could have ordered the hit? Yes, but not every character in "Dragon Ball Super" has a good enough reason to want Goku dead. Champa, for example, has no reason to order Hit to assassinate Goku as the tournament ended in his favor, with Beerus restoring the Earth of Universe 6.
Botamo, the bear-like creature that Goku defeated and Magetta, the iron robot Vegeta defeated, doesn't seem to be smart enough to do it and Cabba seemed to be a good guy. As for Frost, he actually defeated Goku and Hit doesn't seem like he would take orders from Freeza's Universe 6 counterpart.
Vados seemed like a suspicious character, considering that she promised Hit that she would give the traveling Cube that Champa used to travel in between Universes. It's also important to note that since Hit will be traveling to Universe 7 to kill Goku, then it's possible he used the Cube.
But Vados is an angel and they are usually neutral so it's most likely she didn't order the kill as well. So given the information on all existing characters, it's more likely that Beerus and Whis ordered it.