I personally think that is is NOT likely to see Fire and EMS merge any time soon in Upstate SC areas.
The "modern" fire service developed in the 50's and 60's during a time when communities were centered around mill villages, and those mill communities exerted much more control and effect on people's lives than the county government. There is still a lot of segregation, even competition, among fire departments in these counties. And the communities feel like the fire department (and maybe a post office) are the entities that still define those communities now that the mills are long gone. They don't want to give up the unique identity of the community fire department.
I think that has been the big barrier to consolidation of fire departments. It's amazingly inefficient for there to be some many independant fire departments. I bet there are well over 200 different fire department entities among the upstate SC counties - Greenville, Spartanburg, Cherokee, Oconee, Pickens, Anderson, Union and Laurens. It's crazy, really. And many of them are special purpose districts created by the state, with little to no direct relation to the county government at all. Therefore, the county governments would have a very difficult road to try to consolidate fire departments under county control, assuming they wanted to. I believe the county governments are perfectly content to stay out of the fire service, even though citizens could see improved service and lower costs (taxes) if they did.
So, if we assume little consolidation among fire departments, there's little hope that the now-combined county EMS service will merge with the fire service. I don't see EMS trying to parcel out their service to dozens of FDs. It's worth remembering that in Spartanburg, at least, and maybe in other counties, the fire departments ran independent volunteer rescue (ambulance) services for decades in the 1960s-90s. . Those fell away as medical technology and the training required for EMTs and paramedics advanced so much. It was impractical for volunteers to gain and maintain that level of training. That's why we see consolidated EMS service today. Fire departments are also now moving from majority volunteer staffs to professional staffs for the same reason. But I don't see that leading to a lot of consolidation. Fire departments compete for professional firefighters by offering higher salaries and other perks to lure ffs away from other departments, again leading to an "arms race" among departments at the expense of taxpayers.
However, we should see EMS partnering with FDs to share facilities (stations) - that happens now. And they can and should share dispatch services.