There are many ways of saying that something will probably or possibly happen in English.
bound to = certain: "They are bound to succeed!"
sure to = certain: "He is sure to win the championship."
likely to = probable: "We are likely to win the contract."
definite = sure: "He's a definite frontrunner for the job!"
probable: "It's probable that we will be on holiday around then."
likely: "An election is likely next year."
will definitely happen: "There will definitely be a storm later."
will probably happen: "They will probably take on more staff."
may: "We may be able to help you."
might: "There might be a holiday next month - I'm not sure."
could: "There could be a bug in the system."
... is possible: "Do you think he will resign?" "Yes, that's possible."
... is unlikely: "It's unlikely that she will move."
will possibly: "She'll possibly tell us tomorrow."
probably won't: "They probably won't hear until next week."
definitely won't: "I definitely won't go to the party."
... is highly unlikely: "It's highly unlikely that the company will expand."
Note: Be careful of the word order.
"Definitely" and "probably" come after "will" (in positive sentences) and before "won't" in negative sentences.
You can add words to alter the strength of probability:
highly likely / unlikely (= very likely / unlikely)
quite likely / probable / possible (= more likely, probable or possible)
could possibly / probably
most definitely won't (= even more unlikely)
When we want to say what we think will happen in the future, we can either use will followed by the verb without to, or going to followed by the verb.
"What do you think will happen next year?"
"Next week is going to be very busy, I think."
"There won't be a rise in house prices next year."
"He isn't going to win the election."
Speaking tip: Because we also use will to talk about intentions and strong decisions, we often use going to to sound more objective.
"He won't help us" can mean that he has decided not to help us. But "He isn't going to help us" doesn't have this negative implication. It sounds more like a prediction and a simple, objective fact- perhaps he isn't able to help us.
Predictions based on what you know now
We can make predictions based on what we can see now. To do this, we use going to and the verb (not will).
"Watch out! You're going to hit that car in front."
"It's going to be a lovely day today - not a cloud in the sky."