Lot of folks are confused whether they want to downgrade their application or not. It is a tough decision based on whether you need EAD right away or not. Below are some scenarios that might give you an idea on what might happen.
Number of Green Cards issued over the last 10 years taken from various Visa Statistics reports in :
As you can see, the maximum number of green cards issued was 23,997 in FY 2011 for EB2 India. The minimum in the last 10 years was 2,908. Every year, EB2 India gets a minimum of 2,800 per law. That number is out of 140,000. According to , DOS has estimated 261,500 to be given out this year under Employment Based immigrant visa category. So, for EB2 India, it will be minimum 5,230. Same for EB3 India as well.I-485 pending inventory taken from :
EB2 India date was 08-JUL-09 according to September Visa Bulletin .
Assuming, the above inventory data is correct and all the applicants before July have been cleared, the EB2 India final action date should move to 15-DEC-09 to get to 5,230 number. Assuming, about 12,000 folks move to EB3, the date can even move to 08-JUL-12, to get to 23,977. Those might be the worst and best case movements this FY. I believe somewhere in the middle is a good possibility. Lot of unknowns here - what will be the spill over to EB2 India, how many folks move from EB2 to EB3, how many applicants are still pending before 08-Jul-09. Lot of assumptions.
You can keep a watch on visa bulletin movements. Then, depending on your priority date, and depending on what you believe will happen, you can decide whether you want to downgrade your application or not. As always, please do consult an immigration lawyer about your specific situation.
 - Visa Statistics reports - https://travel.state.gov/content/travel/en/legal/visa-law0/visa-statistics.html
 - I-485 pending inventory - https://www.aila.org/infonet/processing-time-reports/eb-i-485-inventory/uscis-i-485-employment-inventory-statistics-7-1-18
 - October 2020 Visa Bulletin - https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2021/visa-bulletin-for-october-2020.html
 - September 2020 Visa Bulletin - https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2020/visa-bulletin-for-september-2020.html