They rightly fear that in 2-3 years, when the pandemic is likely over everywhere and other people have figured out how to commercialize the IP, they won't be the only ones producing their vaccines.
This isn't going to help India or anyone in the short term and there'll be more than enough doses for every person on Earth by next year. Why should they not retain the IP rights to make a profit on new generations that need to be vaccinated or potential booster shots? The manufacturing capacity will have been built up so scarcity won't be a problem at that point.
Is it reasonable to believe that the knowledge that the USA doesn't intend to support the pursuit of damages for patent violation would have an impact on manufacturers now.
If you held a firm conviction that in the near future you'd be able to act on the IP without being in violation, would you be more motivate to progress toward doing so more swiftly?
As a patent holder, would you feel more secure that you could issue cease and desist notices and peruse damages after the waiver is lifted?
Simple, the Indian vaccine factories already have licenses to produce these vaccines but are struggling to scale up production: https://www.bbc.co.uk/news/world-asia-india-55571793 (in part because they can't get some of the supplies needed, which maybe could be helped if the patents for those are also waived and other factories can help to make those...)
This is about mRNA vaccines, but similar things exist for viral vector vaccines as well. Technology transfer, bioreactor bags, fill-finish capacity, all of these things are bottlenecked till next year basically.
This isn't going to help India or anyone in the short term and there'll be more than enough doses for every person on Earth by next year. Why should they not retain the IP rights to make a profit on new generations that need to be vaccinated or potential booster shots? The manufacturing capacity will have been built up so scarcity won't be a problem at that point.