At halving your "profit" doesn't get cut in half. Your Gross income (barring changes in fees) gets cut in half. The difficulty will drop some as negative/marginal players drop out - but ultimately only the leanest players will remain.
Which is why it don't make sense to buy miners before the halving. You are taking a big risk, since there is no solid information what will happen. Price drop, less diff. etc.
But when it comes down to mining in general I don't think it's profitable for the small miner in a year now. Just look at the stats:
https://bitcoinwisdom.com/bitcoin/difficultyToday: 194,254,820,283
1 year ago: 48,807,487,245
That's 4 times more!!!