In bollywood now a trend is going on and that is of launching of fresh female face opposite well established actor. Reason behind this is very simple they want to add an extra element ... and that is fresh element with their story and publicity.
People would love to see new face and also eager to see how they act and their face expression. This may be one more reason which force people to see the movie. Our bollywood is actor based industry and here a well established actor can carry a new actress but a well established actress like Aishwarya, Kareena, Bipasha, Priyanka Chopra or Katrina is unable to carry a fresh male actor.
Producer and Director know that this equation will give a fresh thinking to the viewers and will also fruitful to them as well. Just imagine instead of Anushka sharma if there will be Katrina Kaif, don't you think that this will make your curiosity level down. Thats exactly they capitalised and now getting success.
New actress formula is like launching a fresh bowler against a team. Opponent team do not know anything about that bowler and hence bowler and bowler's team can get a benefit.
I am just waiting to see the performance and impact of next fresh female face and that is Asin.