Is Bitcoin the final form for humanity?
You're underestimating human history, bitcoin is just a footnote in that history in the grand scale of things, I know that you want to sound profound but I'm telling you, it's not in any way makes you, not to mention it's stupid.
Decentralization has long been dreamed by all different social models, is there another step to be taken?
The only social model that I can think of is anarchy and not many people are prepared for that.
Can humanity (humans) learn to hang on and manage their finances?
Another stupid question, of course they can didn't we create banks and didn't we have financial planners?
Or is Bitcoin an experiment to show that we're not capable of managing our own belongings and do require central authority?
Far fetch theory if not crazy overall, you should've read Satoshi's whitepaper, I think it's available online, that's going to answer your question as to why Satoshi created bitcoin.