It really depends on what you mean by Empire. Rome already has extensive dominions; in that sense, the "empire" already existed. If by empire you mean Augustus' specific system of political control, then something like that will develop even though the details may be different.
The Roman constitutional system could no longer hold the ambitions of its top citizens. The inter-elite competition was too much. Rome had gone through several decades of civil wars by the time August assumed power. He was able to rule because of his great political talents and general exhaustion of the polity. All his rivals were dead by that time.
If Pompey wins the civil wars, the basic instability remains. I don't think he has the vision to implement a new constitutional order to resolve the problems. He is likely to keep the peace until he dies, at which point another civil war erupts in another decade or two.
The Senate is increasingly unable to maintain control of public power. Its generals pay for their troops directly, meaning their soldiers owe loyalty to them, not the res publica. The vast wealth brought in by Rome's conquests has corrupted the republic's politics. There is too much at stake now. Furthermore, the political system requires a fierce amount of rivalry aimed at the destruction of political opponents. Lastly, there are serious issues involving the landless which will keep festering things.
I don't see how gradual or peaceful reforms will succeed absent someone of political genius. There will be a war. Someone will eventually win. By winning, he will wipe out a lot of the elites and this will reduce the amount of elite competition within Roman society. That someone will need to control the state so that he can end further bloodshed. That settlement might be worse or better than Augustus, but eventually it must be done.
The Roman constitutional system could no longer hold the ambitions of its top citizens. The inter-elite competition was too much. Rome had gone through several decades of civil wars by the time August assumed power. He was able to rule because of his great political talents and general exhaustion of the polity. All his rivals were dead by that time.
If Pompey wins the civil wars, the basic instability remains. I don't think he has the vision to implement a new constitutional order to resolve the problems. He is likely to keep the peace until he dies, at which point another civil war erupts in another decade or two.
The Senate is increasingly unable to maintain control of public power. Its generals pay for their troops directly, meaning their soldiers owe loyalty to them, not the res publica. The vast wealth brought in by Rome's conquests has corrupted the republic's politics. There is too much at stake now. Furthermore, the political system requires a fierce amount of rivalry aimed at the destruction of political opponents. Lastly, there are serious issues involving the landless which will keep festering things.
I don't see how gradual or peaceful reforms will succeed absent someone of political genius. There will be a war. Someone will eventually win. By winning, he will wipe out a lot of the elites and this will reduce the amount of elite competition within Roman society. That someone will need to control the state so that he can end further bloodshed. That settlement might be worse or better than Augustus, but eventually it must be done.