Iran has somehow slipped completely out from my mind lately but I heard there are frictions inside Iranian leadership. Nuclear bomb in Iranian hands perhaps would lead to official recognition of Israeli nukes from US and nothing more. It would lead also to some sort of uneasy stalemate in the Middle East, but there will be a much needed stability and possibly decline in oil prices.
What the world fears is American desires to prevent such stability from taking place, some hawkish elements in the Western establishment probably think that successful invasion of Iran by US and UK would bring oil price down. Grandious plans or dreams on scale of Alexander of Macedonia.