If this magic "NuCoin" (seriously why nu coin, why not say New Coin, you promoting Tee nucoin?) were to replace bitcoin it wouldnt happen overnight and make bitcoin suddenly worthless.
Bitcoin will always have a value. It had one way back when it first started (although it was tiny, ie 10,000 coins being worth around $40 in 2009) and it will continue to do say way into the foreseeable future.