During Bethesda’s pre-show stream, they stated that any titles that are announced at their E3 press conference can be pre-ordered on Amazon. As of the time of the announcement, both Fallout 76 and Rage 2 were available for pre-order.
Outside of these two titles, nothing is really known about what will be announced during their press conference but if you are interested in pre-ordering any of the titles they do end up announcing, you can do so at the following link:
Amazon/Bethesda Pre-order Page: https://www.amazon.com/b/?node=759766
