What would happen if the EB-5 capital quota increases when my I-526 petition is still under review?

The change will not be applied retroactively to existing cases.

It is unlikely this will happen. Congress needs to make new laws, but by the time Congress finishes its work, your application should be approved already! (Congress is slower than USCIS).

If for some reason the capital quota increases, you will be grandfathered in, provided your application has been filed.

It is unlikely congress will retroactively increase the amount of capital contribution. Generally speaking such changes only impact cases filed after the effective date of the statute.

Currently, there is no expectation that the minimum required investment amount will be $1 million dollars. Assuming that your I-526 petition is being adjudicated with a $500,000.00 investment and during this process the minimum requirement increases to $1 million, then more likely than not, the USCIS regulations will allow you to be grandfathered in with the lower investment requirement.

Currently, there are no plans to change the current $500,000/$1 million structure of the required amount of investment. If this does happen, there would probably be some grandfather clause for pending petitions.

It would take a new law to make such a change (an act of Congress signed into law by the President). Most likely, such change would not be applied retroactively to existing cases.

Nothing, it might take a little longer to get your residence because you will be in a line.

If it changes retroactively you will have to invest more, and if not, you will not have to invest more.