With the recent halving of block rewards, the incentive will be lower than previous for miner. On the other hand, the cost for them will still be same which may not be profitable for a while.
Yes it's true, but miners could also still mine other Altcoins while mining BTC. Regarding in of cost in mining, Bitcoin code has a feature that automatically adjust whenever the mine block time is not reach this means if blocks is getting longer than 10 mins than the difficulty will decrease thus making miners mine faster and solved blocks and getting rewards.