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What is the chance of another Bitcoin-like currency system to replace Bitcoin? Will Bitcoin still coexist with such systems? Will it affect then-current Bitcoin exchange rate?
By Bitcoin-like, I mean, government and banks approved, more privacy, some other means of mining, special purpose (only to buy cars), with different benefits, etc.
5
It's near certain that other Bitcoin-like currencies will continue to be introduced from time to time. Some of them will likely gain some traction.
Over time, more and more deficiencies of Bitcoin will become apparent and newly-designed competitors will be able to fix them. While Bitcoin can certainly make some changes, it will always have a trade-off because significant changes risk shaking to confidence of current users. At some point, Bitcoin's accumulated deficiencies will be too much and it will lose significant share to some competitor.
Of course whether that will be next year or next century, I don't think anybody knows.
Some such systems will likely coexist with Bitcoin without much interaction. Others may design in interaction with Bitcoins directly into their fundamental design. Nobody has a crystal ball though.
Some have imagined high-speed, high-volume systems that would move Bitcoins outside the regular blockchain with the existing Bitcoin system used only to "settle up" large transfers between smaller, faster systems. Will that be what happens? Who knows?
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A currency controlled by a single individual, company or government would not need to work like Bitcoin. It would be centralised - there would be no need for mining, running special clients and so forth. Those are only a key feature of some decentralised internet currencies similar to Bitcoin.
It is possible that such a currency would replace Bitcoin, but it would be done most likely by law and force, rather than because of its benefits. A currency like that might exist alongside Bitcoin, but how much it is used would depend on the appeal and use of it. Should it for example be the only currency you could pay taxes in, it might as well exist for a long time.
There is also an idea of Digital Coin, where many such currencies might exist at the same time because they would be beneficial for the companies and their customers. It has space for Bitcoin-like currency - as a measurement of standard of value, as well as last resort for trading.
All in all, Bitcoin won't probably be replaced, it might be outlawed, and other currencies might exist alongside it.
1Even if new bitcoin-like systems introduced, Bitcoin will have it's advantages, like, user base and first system to scale to this level. – vi.su. – 2012-11-20T02:04:19.590