The one thing to note about Key series that there is certainly going to be plenty of other merchandise out there.
They make so many variations of card sleeves, card boxes, and deck boxes for example - especially of Clannad, Little Busters, Rewrite, and Angel Beats. They are still making new card-oriented items. Just be warned that there is a lot of “swimsuit” level stuff mixed in with just about all of their merchandise, but most Key fans probably know this already.
If Summer Pockets is a major title (and it gets localized, etc. - better to just be safe), then there will be a whole lot more than just a few figures and tapestries, some extra soundtracks and remixes, and art books. In this way, that does make selling that as preorder content seem disappointing but if it sells more copies of the game when it is so hard and so cutthroat to make money in that industry then opposing it seems so counterproductive.
This does make me want to see what that plushie looked like though.