For the Warlympics, Dunga has created a lot of templates on the Warlympic Stadium map. These all have custom scenario distribution, as well as many other details.

I want to know if he will have to re-enter all of these custom scenarios if I update my map. No territories will be altered in any way (other than being enlarged so the army numbers would be smaller).

All of the other details would carry over, but the custom scenarios would not. Unfortunately WarLight doesn't currently have the ability to transfer a custom scenario from one map version to another.