Q. Will doing this, and thereby paying less OR state income tax, increase our federal taxable income for the FOLLOWING year?
Simple answer: No.
But it depends on the details. You are allowed to deduct, on the federal return, state income tax withheld. But you are not required to so, if you know it will only be refunded. Furthermore the state income tax deduction is only an itemized deduction, subject to limits. If you get not tax benefit from entering it on your 2019 tax return, you do not have to report it as income on your 2020 tax return.
If you get a reduced federal tax return in 2020 it generally only balances off the increased 2019 return. I say generally, because taxes are complicated,and changes in total income can sometimes affect refundable tax credits.
If it's bad enough, you can then just file an amended 2019 return and undo it.
