Conveyance of the property

A building in Mumbai is in the process of undergoing redevelopment. The society does not have the conveyance.Conveyance is with the builder who has been appointed to redevelop the property. A huge piece of land was purchased by this builder and this building stands on one part of the bigger land. The builder has always maintained that he will handover the conveyance to the society at the time of possession.This was turned down by the society. Now he has come up with a proposal tht: The society hands over the signed development agreement to him with the condition that he will handover the registered conveyance to the society within a month and the flats will be vacated one month after the conveyance has been received. I want to know that if the development agreement which is time bound is handed over to builder can the builder back out on his promise to hand over the conveyance. If he does what would be the consequences. Is it really very important to have the conveyance before vacating the premises?