It won't ever switch to DPOS or POS. The POW protocol on bitcoin is much more secure than the DPOS protocol used by HIVE. Partly because bitcoin is so large and it is so expensive to attack. We have already seen the vulnerabilities of DPOS with STEEM/HIVE. All you need is a controlling stake or 17 colluding witnesses... both of which are significantly easier to get than it is to attack bitcoin.