When making predictions, we can use adverbs/adjectives to express a

degree of certainty (how sure we are)

People will definitely work longer hours in the future.

People definitely won’t work longer hours in the future.

Other adverbs that are synonymous with definitely: undoubtedly, certainly

You’ll probably enjoy this film.

You probably won’t enjoy this film.

It is likely that you will enjoy this film.

It is unlikely that you will enjoy this film.

(likely is a more formal word that has the same meaning as probably)

Other examples:

I think that robots will do all of the housework in the future.

(I believe, I know, I am sure)