Her next banner is part of Pilgrimage Fest 3.

https://fategrandorder.fandom.com/wiki/Evocation_Festival_Part_3_Summoning_Campaign

We don't have a date. We have estimates based on the order of JP events and campaigns, but those can be moved around, altered or even just skipped. This one isn't likely to be missed, but still, no exact dates until they announce the campaign.

@DeltaBladeX thanks for the info.