If you mean by sued by the cops, that is likely to happen no matter what. Even if one or more of them is found guilty in a jury trial, they will fight to get their jobs back.
Fortunately in that regard all it can cost the city is wages and benefits, plus whatever they spend to defend their actions. They'll pay their city attorneys a few tens of thousands in billable hours and an arbitrator will probably charge them anywhere from $3-10,000 per arbitration and if they win, that's the end of it.
If the cops agree to any plea bargain (assuming they even get charged with crimes, never a sure bet) those plea agreements will almost certainly include taking no administrative action against the city regarding their terminations. The city acted quickly in firing them, albeit I am sure for public relations reasons, but hopefully they have enough evidence to sustain an administrative case against any of them if that becomes necessary.
I know I'd be looking very hard at this kind of rapid, summary judgement if these guys were my members, and I have been on the losing side only twice in the dozens of arbitrations I have brought. Of course I'd sooner starve than work for a police union.