We know that FY 2020 had 156,500 employment based green card (immigrant visas) from [1]. We also know that 261,500 visas are available for FY 2021 from [2]. Based on this, we are projecting the FY 2021 per category numbers in the above table. We know the FY 2019 actual green cards given for each category from [3].
By the spillover rule, unused visas in EB4 and EB5, will go to EB1. Unused visas from EB1 will go to EB2. Unused from EB2 will go to EB3.
Let assume, for all the categories except, EB2 India and EB3 India, we will have the same usage as FY2019 (latest year for which data is available to us).
Given all of this, lets do some calculations for FY2021 projections:
EB4 = 18,567 (FY 2021 availability projection) - 10,088 (FY 2019 actual usage) = 8,479
EB5 = 18,566 (FY 2021 availability projection) - 9,478 (FY 2019 actual usage) = 9,088
EB1 = 74,789(FY 2021 availability projection) - 40,092 (FY 2019 actual usage) = 34,697
Then, EB2 India will be = 74,789 + 2,908 (FY 2019 EB2 India) + 8,479 (EB1 Spillover) + 9,088 (EB5 Spillover) + 34,697 (EB1 spillover) - 40,052 (FY 2019 EB2 Total) = 89,909
By same rule, EB3 India will be = 74,789 + 5,083 (FY 2019 EB3 India) - 40,876 (FY 2019 EB3 Total) = 38,996
It will be a miracle if this happens !!! The above scenario is more for people looking for more positive news.
From Table 2 in [4], we know that, EB1, EB4 and EB5 have backlog more than the available numbers for FY2021. If the processing happens properly, all of the visas available for these categories will be used up. That means, no spill over for EB2. Either way, there is no spill over for EB3 as EB2 is severly backlogged.
The spill over for EB2 India in particular will be determined by EB2 ROW usage. EB3 India spill over will be determined EB3 ROW usage.
-----
[1] FY 2020 Numerical Limits - https://travel.state.gov/content/dam/visas/Statistics/Immigrant-Statistics/Annual%20%20Numerical%20%20Limits%20-%20FY2020.pdf
[2] October 2020 Visa Bulletin - https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2021/visa-bulletin-for-october-2020.html
[3] FY 2019 Actual - https://travel.state.gov/content/dam/visas/Statistics/AnnualReports/FY2019AnnualReport/FY19AnnualReport%20-%20TableV.pdf
[4] Cato research - https://www.cato.org/publications/immigration-research-policy-brief/backlog-skilled-immigrants-tops-1-million-over