As per the press release issued by CBDT on 31st July, 2017, extending the due date for filing of Income Tax Return to 05th August, 2017 had clarified that the returns can be filed even id the aadhar is not linked and by quoting the acknowledgement number of the aadhar application, provided the linking of aadhar needs to be done by 31st of August, 2017 and the the Income Tax return will be processed only after linking of aadhar with PAN.
Please click the link below for the press release.
Karthik & Sunil 