So let's say what happened in the movie gladiator, actually happened. What do you think would have happened next? I think the senate would be in power for about another 100 years at most before another usurper came and declared himself emperor. Also, I think for a period of time, probably like 10 years, there would be no gladiatorial games in the Collosseum, and all gladiators in Rome would have been freed. Btw I put this in the historical events section because its like a historical "what it" scenario.
Th senate would take control for some time(maybe a few decades), but I don't think they would have been able to rise to the challenge and effectivly manage the empire(especially with the upcoming challenges the empire would face). Eventually another general would rise and take power from them, and then who knows, there are so many different ways this could go.