1) When the block reward is gone, miners will get paid from fee!
Current fees are 3% in reward, you will need fees to be 30 times more expensive to give the miners the same revenue and offer in return the same level of protection.
This alone is worth a thing we should give a second thought on, what will be the next phase of transaction fees when all the block reward are no more, could the incentives from transaction fees be satisfactory or give enough income as they have been having of all time, though this is a bitcoin community and i believe one thing is sure, which is the assurance of us crossing whenever we get to that stage.