Hashrate wont continue to rise exponentially forever. At some point it will taper off and the share prices will go up again.
And what exactly is it that will stop hashrate from rising exponentially?
Hashrate increasing faster than Moore's law allows for?
You do understand that Moore's law is just an observation right? For various reasons it works but it can't allow or disallow anything at all...
And hashrate has a long way to go since it will start get limited by Moore's law...