Define 'plunge'? The amazing thing I find is that Bitcoin held at £50 despite stupid journalists proclaiming the end of the currency, it barely went below ( I was watching the price with interest
) and now it's steadily rising again, in fact I'd say it's acting less volatile than it was before because the price movements seem less jumpy. I'd be concerned if it dropped all the way to £1 for sure or even less, but basically in the current economy I think having it stay at £50 - £100 and maintain that for years to come would be the best thing we could hope for.
With the money printing that's going on I suspect Bitcoin will likely end up going much higher though because the central banks just don't know when to quit.