There has been a lot of speculation about Cyborg being in The Flash, although confirmation has never officially come. It makes sense though, especially as Cyborg is a probably a pretty obscure character to those uninitated. More exposure can't hurt.
It seems we have our most official ackowledgement of the character being in the film though… by way of Funkos. This was tweeted out by The Flash director Rick Famuyiwa, he seems to hinting that the script for the film is now done. On top of the script you can clearly see a Flash funko pop, and behind that one, there are some silver feet. You can't be 100% sure, but it absolutely looks like this figure of Cyborg.
— Rick Famuyiwa (@RickFamuyiwa) September 26, 2016
This all seems to make sense, and it is exciting that the film is now getting ready to jump into production. Full speed ahead.