Every two weeks, the difficulty adjusts to try and make a block (on average) every ten minutes. So if, during a two-week period, many more miners started mining on a chain, we can expect faster blocks until the next difficulty period.
It might be the case that the BTC price (or BCH price) keeps rising and mining gear keeps getting better. In that scenario, the BTC or BCH blocks would typically be mined slightly faster than (on average) every ten minutes, because more miners would join during each period. However, BCH being much more profitable than BTC now will of course not last, because more miners will join and then the slower blocks at the next difficulty adjustment will affect their profits.
Does BCH follow the same rules?
It does still involve the difficulty adjusting to produce a block every ten minutes. But if you read my post, you'll understand that it doesn't
always have to take ten minutes to mine a block.
BCH also has an emergency difficulty adjustment in case the blocks are too slow. This is explained in their
ANN thread.