The Strain will end after Season 5, it has been confirmed.
Speaking at the TCA, exec producer Carlton Cuse restated that the FX horror series (which as just been renewed for Season 3) is a five-season story and wont continue into Season 6, or spinoff like The Walking Dead and so many others profitable series.
Assuming the show continues to air one season a year (and is renewed for two further seasons), The Strain will end in 2018.
— TV Guide Magazine (@TVGuideMagazine) August 7, 2015
— Whitney Friedlander (@loislane79) August 7, 2015
— The TCA (@OfficialTCA) August 7, 2015