In practice, it'll probably work out to be sorta like the issue with flu vaccinations, where health organizations will have to predict which strains are likely to be out there and then prepare accordingly.
Still, even if Ebola somehow rapidly evolved to completely ward off the current treatments, it's moreso the technology that created these treatments that's a breakthrough. So, if Ebola adapts, presumably they'd just update the treatments.
That said, the current treatments probably aren't very optimized yet, either. These are early successes; future results seem liable to be much better.