By my reckoning Danny King does not get his fourth away match in until 17 July against Sheffield. His revised average would then apply from 7 days after that.
The deadline for signing is actually the 28th of August as stated by George on Sunday, so we should know who it is soon.
Rule 17.6.4 - No Team changes will be allowed after 28th August with the effective date being 31st August, except for Riders returning to the Team after injury.