If by the time you apply for the VISA with the Canadian High Commission, the IELTS Score expires, you will need to re-appear for the IELTS. The website of CIC says:
IELTS test results taken within last 24 months with overall band not less than 6.0.
So, I believe you would be required to re-appear for the IELTS Exam.
P.S - This is just my understanding of the procedure.