I'm not precisely sure what you're referring to as "the change" here. The rate of expansion is increasing continuously though, if that's what you're asking.
As far as the measurability of the speed of light, I don't think anything changes in principle. It should remain measurable and constant. However, it gets a lot more complicated in practice, since it's pretty unclear who or what would actually be doing the measuring and how they might go about it.
As far as the measurability of the speed of light, I don't think anything changes in principle. It should remain measurable and constant. However, it gets a lot more complicated in practice, since it's pretty unclear who or what would actually be doing the measuring and how they might go about it.