Hi,
The next offer similar to Ignite has not been announced yet. It will likely be for the Microsoft Build event which happened in May last year, so might be in May of this year.
Right now you can get 50% discount on some Associate and Expert certifications by completing 30 Days to Learn It challenge:
https://developer.microsoft.com/en-US/offers/30-days-to-learn-it
You may also get 100% discount on Teams Administrator Associate exam via Microsoft Virtual Training Days. Here is one upcoming session:
https://mktoevents.com/Microsoft+Event/377908/157-GQE-382?source=mvtd
If the above is helpful please click Accept Answer.
Thanks.
-TP