
Hi, can I use جاء instead of أتى in this sentence? How would it be?

In this case, the verb will be سأجيء,
I believe.

Yes, I've just looked it up. It's the correct verb form.
https://en.wiktionary.org/wiki/...AC%D9%8A%D8%A1

I see. Thank you.

It seems like arabs don't use جاء in present or future tense at all. At least two natives told me it.

Indeed. I believe I have never encountered it either in the present or the future tense. This is why I wasn't sure about the conjugation and had to check myself afterwards.