Why would tax refund from itemized deductions be taxable income next year? How to determine if anything what part of the refund is taxable?

A federal tax refund is not taxable income on your federal return.  A state or local income tax refund is taxable income on your federal return if you itemized deductions the previous year and deducted those taxes.  If you took the standard deduction the previous year, the refund would not be taxable.