I've had both issues, grip of death and proximity sensor, but my feather case solved the reception issue. I also know when I am on a call to make sure I don't move the phone around a whole lot while talking, because this is when you'll hang up, mute, or whatever. Being aware of it, helps me to prevent it.
Hopefully a software update will indeed solve that issue. Not sure the reception issue will be resolved by an update, other than they make the changes Apple has mentioned in regards to bars. It won't change anything in terms of drop calls. So, if you are having drop calls now, you'll likely have them after the update. If you aren't having them now you won't after the update.. I hope!