When Bitcoin gets to a stage where the mined supply is basically 21m (that is, very little remaining btc left to be mined), will Bitcoin still remain a secure network?
If you mean that miners will not be interested in providing us with security and network,I think that they will still be interested in it. To my mind, when Bitcoin reaches its max total supply, miners will get just our commissions for running our transactions, but not new bitcoins as they do now. So there will still be people who want to be miners. To sum up, we shouldn’t be scared.