他一定会来。

He is sure to come.; He will surely come.

《新英汉大辞典》

除非他有急事要办，不然他一定会来。

He is sure to come unless he has some urgent work to do.

youdao

如果可能的话，他一定会来。

He will come if he can.

youdao

As far as I know we're getting him, so I hope that you will all be able to come this Friday, here, at the usual time.

我知道他一定会来,所以我希望你们周五也能来,老时间,老地点

耶鲁公开课 - 金融市场课程节选

We would have to see if we can arrange that. Again, I don't guarantee that it will happen because the reality is, someone who is involved in as many things as he is-- it's going to be something.

我会再去安排一下,但我不保证他一定会来,他有太多的安排,有可能会有突发情况

耶鲁公开课 - 金融市场课程节选