Evidenced by everything in the last season with Abra Kadabra and 2024 Barry from the timeline where Iris died, DeVoe faced Barry and lost. The future of 2024 we saw in "The Once and Future Flash" has a lot of inconsistincies with the events of Season 4, that's saying if we imagined what it would've been like if Iris died. 

  • Julian never moved back to England even when Caitlin was still Killer Frost. 
  • Joe and Cecile never had a kid together.
  • Ralph was never seen mentioned or fighting as a hero. 

Speaking of Ralph, this could be explained. Sure he was brought back from the dead after Flashpoint, but how he got his powers is thanks to Savitar's errasure from existence. Barry took his place in the Speed Force, but DeVoe used the Samuroid to pressure Team Flash to bring him back, infecting the bus-metas with Speed Force-induced dark matter.

It remains to be seen how different DeVoe's plan would've been if Iris had died, since her not dying is what retconned Savitar and so on..., it's not like the smartest man on the Earth wouldn't have found another way to make metas of his own and take advantage of a heartbroken speedster who lost the love of his life.