The batting is a smaller problem. Rohit Sharma for example has had a superb few months in the limelight of T20 and before that, did very well in the first class season. His form in ODI cricket has been less than stellar but it would be premature to write him off so quickly. I maintain that among all the new Indian batsmen - Raina, Pujara, Rohit Sharma, Rahane and co., he is the classiest batsman and is most likely to end up with 20 Test hundreds by the end of his career.
The problems faced by this generation of batsmen are more complicated than say those faced by Tendulkar or even Ganguly & Dravid 7 years later. The craft of batting in ODI cricket has changed over the past 3-4 years, the craft of batting in T20 is only just emerging, while the craft of batting in a first class game or Test Match still endures. Ironically, the most adverse effect of T20 cricket is likely to be on ODI batting, and not on First Class or Test Match batting, because both T20 and ODIs tend to begin at the same frenetic shot-a-ball pace. The catch in ODI's is that a batsman, especially a top-order batsman, still has to build a proper innings over 30-35 overs (ideally more). The pace in the first few overs of the ODI must be set keeping this in mind. There is also the time honored truth about a batsman's first mistake being the only one he is permitted in most cases.
This is where Tendulkar will be missed by India. Not for the big runs that he makes, for India have enough firepower in the middle order to make runs, but for his mastery of these early overs. His ability to judge the bowling, the wicket and the match situation and adjust. How well does he do this? Lets look at his record. In 303 innings as an ODI opener, Tendulkar has made 13568 runs at 48.11 with 39 centuries and 70 fifties. His strike rate is 88 runs/100 balls. So in 109 out of 303 (or slightly better than 1 in 3) innings, Tendulkar reaches 50. He faces on average 51 balls per ODI innings. He has reached at least 30 in 163 out of those 303 innings. He has survived 30 deliveries (half of 10 overs) 172 times in 303 innings or 57%.
Compare that with say Adam Gilchrist. 9200 runs at 36.50 (strike 98.02) with 16 centuries and 53 fifties in 259 innings as an ODI opener. Gilchrist reaches at least 50 once every 3.75 innings (for Tendulkar this figure is 2.77 innings). Gilchrist has survived 30 deliveries in 128 of his 259 innings or 49%.
Surviving 30 deliveries is one thing. How often does Gilchrist reach a score of 30? 119 times in 259 innings (46% of his innings). How often does Tendulkar? 54% of the time.
Comparing Gilchrist and Tendulkar is instructive, because they were different types of ODI opener. Gilchrist, in theory, did not bear the burden of shouldering his teams innings to the extent that Tendulkar did. Gilchrist did not open the batting because he was the best batsman in the Australian side. Tendulkar did it because of a simple reason - he was the best batsman in the Indian side, and so it made sense for India to have him face as many of the 50 overs as possible. This argument has not changed much over 15 years, even though the later batting has definitely been superior in this decade. Given this role, Tendulkar has more than met the targets set for him by the Indian side. As has Gilchrist for Australia.
But India's batting strength, which has been the basis of their success (given the moderate pace attack) has been built on Tendulkar managing the early overs (with Ganguly for a few years and then with Sehwag). The absence of Tendulkar may not become apparent on a game by game basis, but if you look back on a year or two without Tendulkar (which will soon become possible), you will most likely find that the Indian batting performance in ODI cricket is poorer over such a period than you are accustomed to, despite the middle order doing very well.
There are those who argue that Tendulkar has merely benefited from the easiest scoring period in a limited overs game. They do so by citing the fielding restrictions that come with the new ball. Of course, they don't take into account the new ball, fresh bowlers, fresh fielders, and most crucially, Tendulkar's game plan and the tactical expectation from the team which says he should try and bat for 50 overs. Seen in this light, Tendulkar's early assaults are fraught with greater risk than say Gilchrist's (i want to also say Jayasurya's but im not completely convinced that Jayasurya's role in the SL batting, despite his methods, is anything like Gilchrist's).
It is a complicated task, and Tendulkar has for almost 15 years, single handedly borne this large chunk of India's limited overs batting workload. He has done it with aplomb. It remains to be seen whether Gambhir and Sehwag can do his job, or whether the job will be retired with Tendulkar and future Indian ODI opening batsmen take up more Gilchristian roles.
I remain convinced that a successful ODI batting lineup is built around one crucial batsman in the top 3 (Gilchrist had the luxury of having the amazingly consistent Ponting at number 3). Whatever strategy India choose, they will have to find a great player in at least one of those three positions if they are to maintain their recent batting performances in ODI cricket.
Yuvraj Singh has emerged in the middle order for India and surpassed his predecessors. Dhoni has emerged as the most astonishing floater in limited overs cricket (4521 runs at 49.68, strike rate 90!). India need to find the player who will take over Tendulkar's job. So far, this batsman has not emerged.
Of course, if India find a couple of crack pace bowlers, everything would change. But then again, that has proved elusive...