eliphas8 has it right, the only long-term alternative to Kerensky being overthrown by Bolsheviks is being overthrown by the right-wing forces. However, if Kerensky had been a different sort of man, I think he could have held onto power. His exact motives have always been sort of mysterious from my perspective; in my opinion it seems that he was angling to become a populist dictator, but lacked the perspective, wisdom, and most importantly the ability to inspire fear (in the Machiavellian sense) to keep the nation in line during the critical first months of his rule. Kerensky's oratory was from all reports remarkable, and he did have charisma, but unfortunately his chief talents seemed to have been reckless intrigue and alienating people who should have been staunch allies.
I've been reading a lot on the October Revolution and the subsequent Civil war for the past few month, and what strikes me was just how badly the Provisional Government botched things from the moment they took over. Things were not necessarily heading towards a state of unraveling initially; it took a lot of bad decisions made in a short period of time to bring things to the crisis that allowed the Bolsheviks to launch their coup. If the Provisional Government had made even one good decision during the whole chain of events, the Soviet Union would likely never have been formed, and there was a good chance Russia could have come out of the period far less damaged. There would have been other big issues to confront, in regards to education, healthcare, land reform, and autonomy for the various ethnic groups, but I think they were resolvable in the long term.
Keep in mind, the Bolsheviks under Lenin managed to keep control of the central zone of Russia despite their initial incompetence and utter brutality to the locals, and by doing so were able to reconquer a good 90% of the territory of the Russian Empire within half a decade. It is not hard to imagine a group with the same determination but better methods could have taken everything back except for Congress Poland at a fraction of the cost in the OTL.
I have been working on a timeline that focuses on a military junta that works with elements of the civilian establishment to establish a "Unity" government. Through imperfect, their relative competence allows Russia to work through 1917-19 with far less fighting and disruption of Russia's social and economic structure. It would have major implications for how Russia handles the run up to WWII. It still has a lot of work needed before it's ready for posting however.