Bitcoin is surely a path-braking innovation from Mr. Satoshi, but with due respect, I strongly believe that bitcoin doesn't have the power to replace the century old banking system. Bitcoin probably can introduce a new digital era of currency to the mankind, but can't replace the fiat.
And what happens when a new era of currency appears? It replaces the old one. It makes the previous one obsolete. I don't know if you realize this but you're actually contradicting yourself.
Also I strongly believe that bitcoin is best at its current form. but if it tries to break of the fiat currency system or try to introduce a regularized currency system, it will be destroyed in no time. People are enjoying bitcoin because of its high pricing potential and anonymity. If anything goes wrong, people will not take time forget bitcoin and search for alternate.
Bitcoin wouldn't "try" to break fiat system. The fiat system will automatically be broken when bitcoin finally become mainstream. Who says bitcoin will be a regulated currency? Like you said, it would be destroyed when it did that. So it definitely wouldn't do it. Being decentralized and unregulated is the essence of bitcoin, removing any of those features will not make bitcoin any different from the fiat that we know right now.