In test matches, I think Sreesanth and Munaf Patel are solid. RP Singh is pretty good when in form and the A team stints should help him a great deal. In one-day matches, Agarkar is the veteran who has shown newfound consistency and maturity lately. RP Singh and VRV Singh are both going to be given their chances for some time.
As for Zaheer, he has been given plenty of chances and he hasn't looked threatening for India recently. If he can finish the English domestic season as a leading wicket-taker and do well for Baroda next season, he may have a chance to stage a late comeback. I don't think he has any place in the World Cup plans; it's just too late and we've committed to six pacers: Pathan, Sreesanth, Munaf, Agarkar, RP and VRV.
As for Balaji and Nehra, they were both reported to have recovered from the injury and started bowling again. Balaji is young so he could return next year. Nehra was pretty impressive just before he got injured and I think he can still be a strike bowler for India in ODIs. It will still be tough for them with the emergence of guys like Sreesanth, Munaf, VRV, Nabi, Trivedi, Yomahesh, Paul, etc.
All this assumes that the Indian selectors use their brain when considering players and choosing teams. That is no guarantee.