So our return is already submitted and will go to the IRS on 1/12. What happens if our return is accepted and then Biden's plan is approved that includes raising the child tax credit. Will tax forms

Have you ever heard the expression "Don't count your chickens before they hatch"?

Congress has not voted on a 3rd stimulus plan and has not voted to increase the child tax credit.  No one knows when or if they will, nor do we know how it would be implemented.    We can just wait to see what they do and see what the guidelines are someday.

We don't have specific information on the income qualifications or procedures for the third stimulus payment because the measure hasn't been passed yet. However, If you had issues receiving your earlier stimulus, then the best way to ensure that you are one of the first to receive any future stimulus payments is to file your 2020 tax return as early as possible and use direct deposit so that the IRS will have your updated information.

You can find the most up to date information from the IRS here, and updates from TurboTax here as they develop.