Bitcoin's security against double-spending is proportional to how many clock cycles are spent mining, which is affected by the price of Bitcoin. A parallel network with a far lower market cap would be less secure.

$1000 per coin is speculation, but it's not particularly different from a startup people are buying into purely because of where it might be in five to ten years. The effect on Bitcoin is magnified somewhat because the maximum number of shares is capped.

Unless something radically better than Bitcoin comes along, I don't see it being replaced any time soon.