Do you think the unraveling of the US empire will bring a final solution to the exploitation problem?

No, for that we would need the real world revolution and then possibly decades of changes. But the US hegemony is stopping any changes in that direction globally with their imperialism.

I fear that the end of the US would create a power vacuum to be filled by another hegemonic empire.

I don't think it's possible currently. US hegemony didn't just popped in existence, it required century of buildup with some huge milestones like industrialisation and colonisation, Monroe Doctrine, WW2 and subsequent dollarisation etc.

Most likely outcome is multipolar world with several centres.