Yes that's totally logical to do but what is going to happen to groups that already got more than 90 members for the meantime?
I don't see it necessary just because of the playercount drops, because in summer the playercount will be 300-400 players once again, it's like that every year.Anyways, we barely see new groups nowadays, most of people wouldn't bother to create a group right now, levels can be gained after months for the groups that are newly created, so if you want to help them out, you should make them level up more easier and not let them wait for months just to achieve one level.As you can see, from L2 to L3 group takes 2-3 months, why's that? if the group is ready for that, why do they have to wait? if it's 1 month, that would be fine, consider this and you might see new groups.Decreasing members limit to 90 won't help new groups anyhow, because people prefer to join the higher leveled groups.