Mark my words,
if the network proves to be resilient to price manipulation, and constant daily attacks, Bitcoins will be worth well over $1,000 a pop.
This is all a big IF ! People can only mine at a loss for SO long. People signing off, only makes the chances for a 51% attack that much more likely.
I hear this claim a lot. I don't agree.
Reduced mining power will actually reduce a 51% attack risk. The biggest risk for a 51% is the big pools being hijacked, or colluding with one another to mount such an attack.
With cheaper, more powerful sha256 block mining devices (FPGA & Structured ASICs) coming online, a reduction in total network power from inefficient GPU mining provides the opportunity for many smaller pools and even individual mining efforts. Additionally, these devices won't be able to replace GPU mining all at once, because there are production and sourcing limits, so there will be a continued slow attrition of GPU miners, until the last one is squeezed out.