Elmer, since current law gives that tax deduction for the imaginary cost of the options, I will speculate that FASB can write the rule so that it is revenue neutral for the IRS. In other words, currently companies deduct the option 'cost' from their profits when they calculate taxes. With this rule change they would no longer be able to apply this deduction afterwards because it already applied before the profit number is established.
Now, I am certainly not a tax expert, just trying to understand the implications of all this. If there is a tax accounting expert who would like to chime in...