No mention of when.
Next up is Georgia GOP Convention on Saturday, June 10 in Columbus. So SC figures the next weekend...
The RSBN website says: The location and date of Trump’s upcoming rally in South Carolina will be announced soon.
https://www.rsbnetwork.com/news/trump-announces-next-rally-invites-patriotic-childrens-choir-that-was-kicked-out-of-capitol/