If India tries to establish a significant military position in Afghanistan post ISAF, its forces will become the new Taliban target. This is a highly inadvisable course for the Indian government to take. They cannot come close to doing what NATO and dozens of countries put together have thus-far failed at.
The recent change of heart Karzai seems to be having, with the sacking of pro Northern Alliance officials, the announcement regarding Afghan military officials being trained in Pakistan and the more conciliatory tone towards Pakhtun groups, seems to imply that allowing or encouraging India to gain a toehold in Afghanistan will serve his interests either.