When will the next Mega Discount event take place?

The summer sale just ended a couple of days ago, July 9, so we'll probably see another sale in the next month or so. They happen pretty frequently.

In the meantime you may want to consider the stack and save discount for Expansion Packs.

Sims 4 Stack & Save

There are some kits that are being advertised on the Marketplace for less moola than usual. I laughed at that, because although there are kits I may want, I refuse to purchase moola.

I'm waiting for Adventure Awaits to go 50% too. Wonder when will it be.