Insomniac Games had a few plans that never came to fruition, as Sony had different ideas altogether.
Colin Moriarty said the following on the newest episode of the Sacred Symbols podcast: „Resistance 4 was pitched to [PlayStation by Insomniac Games] and […] they declined Resistance 4 because it sounded too similar to The Last of Us [developed by Naughty Dog] and they didn’t want the two games overlapping with each other. So, Resistance was shut down at that point.”
Resistance: Fall of Man launched in November 2006 (North America) and March 2007 (Europe), respectively, as a PlayStation 3 launch title. In this sci-fi FPS, Nathan Hale joined a human resistance force to eliminate the Chimera, an alien race that invaded the United Kingdom. However, the story doesn’t end here: Hale goes stateside to the United States, with the Chimera virus inside him. He is part of an elite squad called The Sentinels, and he fights the aliens again in Resistance 2 (which launched in November 2008). Perhaps it’s not too easy to keep the virus at bay…
The third game in the series shifted to a post-apocalyptic tone: Resistance 3, which arrived in 2011 with 3D and PlayStation Move support, replaces Hale with Joseph Capelli. There were two handheld games, too: in 2009, the PSP received Resistance: Retribution (where James Grayson tries to help Europe get rid of the Chimera), and the last Resistance game up to date came in 2012 when the PlayStation Vita received Resistance: Burning Skies (where Tom Riley fights on the east coast of the United States).
After all this, it seems Sony doesn’t want to bother about this IP anymore. Insomniac Games has since moved to Spider-Man, which got so successful that Sony bought the studio. Their newest game, Ratchet & Clank: Rift Apart, will launch on June 11, exclusively on PlayStation 5.