simple. the same way indian and pakistani fans thougth their teams had a realistic shot at the 07 championship: its called over-optimism.
but if you look at the distance travelled by BD from 03 to 07 and project that for 07-11, then it makes a lot of sense.
whether that improve keeps going at the same average rate is a completely different assumption, however.
Bangladesh is a stronger team with Shakib al Hasan.
Bangladesh is a stronger team without Shakib al Hasan.