Block reward is constant, it's just that difficulty increasing makes it harder for an individual to get a block.  If you get one though, you will always get the same amount of coins (3.72 AIR, unless you happen to get a bonus  + 0.001 AIR from redistributed security fees).  As difficulty climbs, you'll need to join a pool (even if you have monstrous hashpower, which just allows you to mine AIR longer solo), which pretty much just gives you the reward you would get on your own based on the pool's settings, except it's not an all-or-nothing deal.  With a pool, you can get part of a block as a reward, which in a sense, is kind of like altering the block reward.