This is part of why it takes much longer for mining rewards to be confirmed than other payments.

Since most people mine as part of pools these days, it probably doesn't matter too much. The average rate for the pool won't be affected too much (though I suppose pools which have been on the 0.8 block chain will hurt a little bit). There may be a one or two individuals who have mined a block and lose out by this, but if so, they were rolling the dice anyhow by mining outside of a pool; you can't expect a consistent income by mining over a span of 13 blocks.