Bitcoin is what it is largely because of mining. Switching to POS would be disasterous.
That's what I used to think but I'm not so sure now. What does mining provide that POS wouldn't?
The fact that obtaining a machine capable to mine the currency costs money and isn't accessible to anyone adds value to it in and of itself. Removing this attribute of bitcoin could take away a big part of the economy that has formed around it and cause massive loss of interest.