Your intuition was correct that something was off with the second sentence. "Has the future" is not idiomatic English in this context. Machine learning does not possess ("have") the future. The use of "have believed" in your first example is the present perfect form of the verb "to believe". It is not using "to have" in the sense of possession. In that sentence the verb have is modifying the verb "believed", and indicates that the belief has spanned a period of time up until the present (as opposed to being an action that was completed in the past).

Either of the following would be correct ways of expressing the idea that machine learning will be important/significant in the future:

• I've assumed that machine learning is the future since I was at that conference.
• I've assumed that machine learning will be the future since I was at that conference.

The only place I can think of that "has the future" would be appropriate to use would be something like "She has the future all planned out." or "He has the future soccer games to look forward to." But this is a very different meaning/context from the usage of "is the future" above.

Your intuition was correct that something was off with the second sentence. "Has the future" is not idiomatic English in this context. Machine learning does not possess ("have") the future. The use of "have believed" in your first example is the present perfect form of the verb "to believe". It is not using "to have" in the sense of possession. In that sentence the verb "have" is an auxiliary verb modifying the verb "believed", and indicates that the belief has spanned a period of time up until the present (as opposed to being an action that was completed in the past).

Either of the following would be correct ways of expressing the idea that machine learning will be important/significant in the future:

• I've assumed that machine learning is the future since I was at that conference.
• I've assumed that machine learning will be the future since I was at that conference.

The only place I can think of that "has the future" would be appropriate to use would be something like "She has the future all planned out." or "He has the future soccer games to look forward to." But in both of these sentences the verb "to have" is being used in the sense of possession (having plans, having something to look forward to, etc).