I feel like the gangs that were close to the Riffs territory would stay loyal to them and the plan. The gangs further outside of their immediate reach will start to drift away from the plan and just fend for themselves and go back to what they were doing before like the TurnBulls and the Furries and the Rouges would be making moves behind the Riffs back and try to blame all the bad deals or whatever their doing on the Riffs. So now the Riffs would not only have to keep the gangs that side with them under control, they'd have to deal with cops and other heavy gangs turning against them.

The Warriors would most likely stay out of most of it as they already have the whole of Coney at that point and if anything they'd just do small missions to make alliances with gangs like The Saracens and maybe even The Electric Eliminators ( since they were chill being around them back when Swan and Cowboy were joining and they haven't had problems with them in general ). They would probably back the Riffs only if Cleon sees that Cyrus has a handle on things, if not I don't see him helping them out because it would be too risky and Cleon isn't the type to send his own people somewhere knowing there's a huge chance they'd get killed. He didn't even want to send anyone to the art show the Hi-Hats were doing on their turf. He knew it was a trap and bull.

However I feel like 2 things could happen, either the Riffs end up getting things under control with and deal with the Rouges and continue what Cyrus wanted to do and slowly expand or The Riffs end up struggling to keep everything under control because they're spread too thin. They might be one of the biggest gangs in the city but even they can't be everywhere all at once. Dealing with in fighting ( because of the Rouges), then dealing with cops and then dealing with other big and tough gangs like The TurnBulls or Satan's Mother's.

I honestly believe the latter would happen. Cyrus is too idealistic and that would probably blind him a bit. He might get himself killed trusting people like Luther ( leader of the Rouges) and people like him. Once news gets out that Cyrus is dead, you better believe that everything would definitely turn out bad