Hi mesan123 (aren't you the infamous n*5 + 123?) jk
I can help you with this:
First, I would suggest that you think and rethink before planning to go for visa stamping.Almost all of the people I know who had gone back to India for stamping have been stuck there for more than 3 months or so under admin processing.So unless you have a compeling reason to do this, I would suggest to avoid. If you do have a valid visa right now on your passport (and depending on your travel back date), I would suggest to use that valid visa to re-enter instead of applying for visa extension at the consulate.
Second, if you are still planning to go for visa, you can submit BOTH the current and new petition at the consulate. I had done the same back in 2008. On the form, I had mentioned the current petition and when I went to the consulate i submitted both of them. Once the officer said my visa is approved, I asked him what the expiry date would be for the visa. He confirmed that it would be according to the new petition. This was back in 2008 - who knows whether they will care to even respond nowadays.
Good luck...