In my opinion, the major impact of the Lucknow Pact was that it helped to undermine British rule in what was then called India. Of course, independence did not come for about 30 more years, but this pact helped bring it about.
Before the pact was signed, the Muslim League was generally supportive of British rule in India. They felt that India would be too pro-Hindi without British rule and that this would harm Muslims in India. When the League signed the Lucknow Pact, this changed. Now neither of the major political organizations in India supported British rule.