In October 2008, the Indian Navy issued a Request for Information (RFI) to a number of foreign shipyards and design firms for construction of a class of advanced diesel-electric submarines. The RFIs were sent to
Rosoboronexport, Armaris and HDW , among others. [1][4] Originally the navy intended to purchase two submarines directly from the foreign vendor, with four licence-built at chosen local Indian shipyards in order to save time. [5] Acceptance of Necessity was accorded to the project by the Defence Acquisition Council in August 2010. [6] In December 2014, the new NDA government fast-tracked the bidding process for Project 75I due to mounting concerns over increasing People's Liberation Army Navy activities in the Indian Ocean region. [1][7] and diminishing submarine strength of the Indian navy. [8] Later it was decided to construct all six submarines in Indian shipyards in accordance with the Make in India initiative of the government.
so that's already almost 10years . don't you think it'll take another 4years to keel laying of first sub (if they sign project this year)
above info from Wikipedia