The Telegraph has laid out a long and detailed discussion of whether Bush is prepared to bomb Iran. To me, it seems just a case of contingency planning being leaked and then evaluated, which is not a bad thing in and of itself (the lead is, but not the evaluation). But, it should be remembered that such planning is on-going for nearly every conceivable possibility, and so the planning for a war with Iran would be just one of many.
It's a long piece, but worth the time. I won't quote anything here, because there's just too much to choose from. Give it a read.