Ok, first of all to the question at hand, I think either anarchism or some kind of christian socialism would become the dominant socialist ideology, the anarchist one being MUCH more likely, since it was for a time the dominant one and still held much influence over a bigger part of the internationale labour movement until well after the Soviet "revolution". The only other possibility, which so far no one has mentioned, might be someone like August Willich becoming more influential in the exiled german labour movmement, making an alliance of democrats and all kinds of communists more viable. For those who don't know, Engels was the Aide when Willich led an army in the 1848 revolution, trying to overthrow and exile royality in some german states. He was also thought Marx was too conservative and challenged him to a fight. Without Marx, I could see him and Engels becoming closer and together, forging a cooperation between democratic forces and communist forces, maybe even with the integration of anarchists. (I cant see Blanqui becoming popular longterm)
On the question of Lenin and marxism: Do any of you actually know what Lenin did or do ya'll just read "Yeah, Lenin was communist thus everything he did was good". Like, he used the states power to fight against working class institutions, like the factory comittees or the soviets or the trade unions. He himself proclaimed the party the vanguard of the working class, but thats like, a+ advertisment, nothing else. At the end, the Leninist experiment failed, as it was destined to and as it was predicted by basically every other marxist or socialist overall. Seriously, some people read Lenin, think they read Marx and then read the communist manifesto and think they got it all figured out.
Anark The State is Counter-Revolutionary 8/10/2020
theanarchistlibrary.org
Have fun reading how the leninists fought against the working class control in "the name of the working class". Fucking sad. The revolution had potential, but faulty political theory doomed it, or maybe just lust for power due to fetishization of state power over workers power.