On what grounds can Epic un-licence my product?

I have a question, if Epic for some reason decides to revoke the license on my product, can they just do that? Or are they only allowed to do it when there is a breach in their EULA?

Only if you violate the terms of the license. There’s some other things though-for example the game Hatred was bared from using the UE logo to promote their game because of the violent content.

I’m pretty sure you can’t use the UE4 to create military technology, so no UE4 combat simulator for my friends over in North Korea I’m afraid.

so If I understood correctly, Epic cannot un-licence my product just because they feel like it right? Can I sue them if they did?

Technically they can, and no you cannot.

Realistically, they won’t unless you’re doing something particularly outrageous.

As far as the licensing terms go, they can adjust the terms at any time, but they will give you an opportunity to agree to the new terms. If you don’t then you can’t access any of their services so you wouldn’t be able to download the editor again. You’d still be under the license terms that you originally agreed to.