Decentralization and stability of price in a short period of time is impossible due the very fundamentals of a free unregulated market such as Bitcoin's. The only way Bitcoin can reach stability is when there is so many people using it that a whale dumping tons of coin would be like pissing on a sea of pee.
When Bitcoin reaches mainstream usage it will naturally stop being so volatile. I don't believe in alternatives to Bitcoin, everything that's needed Bitcoin has it.