The price of altcoin and Bitcoin price never be stable because the Bitcoin price is unstable and it will affect the price of other altcoins. Bitcoin price will always affect the price of altcoins which nothing will be in our hands, we have to move according to the price of Bitcoin and altcoin for purchases and selling.
This is a decentralized market and that will always bring about the volatility. As long as a market is pegged in trading pair against another currency pair, then there is definitely not going to be any form of stability and if by stability what anyone is referring to is having something that would not fluctuate hugely and rapidly, then I would say for a young market, we are not even close yet, and before we can start seeing something like that, I guess we will have to look forward to real life usage.
You wont encourage it if the crypto values are going to be stable. No investors would pitch in if the values are going to be stable.
Upward fluctuation in long term is the reason why most people are here and still holding their bitcoins, however bitcoin may attain stable value like gold (not exact stable yet less volatility) but it may take more decades of time.