Thanks for your work so far. It is greatly appreciated that you spent your time doing this mostly cute and wholesome series.
I do agree deleting the chapters wouldn't be the best decision. If you're going to delete them, doing it a month before the official release (if it really is going to be on May 2020) would be better, since else you're just letting people who come looking for the translated version here, yet don't find it, to look for it in an aggregator site (giving them additional ad-revenue from the visits) while the official release comes out. And even then, they would still go for the aggregator sites when they realize how much there is translated online vs how much the official release does have when it comes out.
In that case, the best decision (IMO) would be to delete the chapters a month in advance before the official version of the volume they're in is released, since that way people wouldn't need to wait for the official release of something that's already translated (and end up going to an aggregator site), but also they'd be encouraged to find the chapters that are already available in the official release (since they'd only have the later chapters to go by, and people usually want to know what happens beforehand).
Nonetheless, that's just my opinion. You have all the right to decide what would be better to do, since you're the ones that would be in trouble if Seven Seas contacted you about the translations, but I'd think the arrangement above would do as much good for both parties as it can be done, in the current state of affairs.