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?
Bitcoin was already a stable and secured network which has been tested many times, yet many controversial issues from different opposing groups who wanted to grab btc down but failed so much. They didn't want bitcoin to be recognized, and what's happening now is a big slap to their face.
All the proofs have been given to all individuals who's still having doubts, so I advise to have short reviews at coinmarketcap and you'll see it as # 1 in the rank.