As per reports from Montreal french radio 98.5 FM, Stade Saputo will not be ready as per the initial plans and you might get to see more games at Olympic Stadium deep in the summer. Originally planning to play 6 games at the Olympic Stadium (including the 1-1 tie vs The Chicago Fire), the Montreal Impact might not even play at Stade Saputo before August 2012. The report comes from an anonymous construction worker as per 98.5 FM. You can read the article at the following link.
As we write this piece, the Montreal Impact already came out with a ''press release'' / statement
Stade Saputo: Nous sommes toujours sur le même calendrier de construction. L'échéancier est serré, mais on maintient le cap sur le 16 juin.— Impact de Montréal (@impactmontreal) March 20, 2012
Basically, The Montreal Impact is stating that the construction deadlines will still be met. The date of June 16th 2012 is still the target date for Stade Saputo.