To me it's a joke to cricket he is currently the best, good short balls can't be left alone a player like gambhir should face a nightmare everytime he goes out to bat with his obvious weakness.
I personally don't know where India is going to be in a few years, the bowlers aren't good and with Tendulkar, Dravid, Khan all gearing up to leave the replacements don't look too promising. All the new batsmen can't short balls, well blame the dead pitches in India that don't encourage short pitched deliveries which results in their best batsman being unable to play them well.
To me the best batsman in the world should not have such a fundamental weakness.
Well the ICC ranking that you are talking about is a ranking on form, not on class...Even I don't think he's the best batsman on class, no way...So, we agree on that point...
But yes, I do believe that good short pitch delveries can be left alone (of course not by all) by batsmen who are good at it...And Gambhir is one of them...
And about India's future, don't worry mate. We'll remain a good side after Sachin, Dravid and Khan leaves...As far as bowling goes, India's bowling is not the best in the world currently; and it's gonna get better only (definitely spin bowling, and quite likely pace department too)...Batting also won't get affected much (of course, players like Sachin aren't born every year) as I'm sure some of the guys among Badri, Kohli, Raina (and definitely Gambhir) will mature with time...
Whether India will remain no. 1 test side, only time can tell. But I have no doubt in my mind that we'll remain a very good side and among the top sides in the world...
And finally, I believe the best batsman in the world might have a weakness. But he should know how not to get out again and again because of that weakness...