Suppose my 2020 income is $25k, and I have $15k in unrealized long-term capital gains in shares of company X. In 2021 and beyond, I expect my income to be $40k+. I consider the shares of company Y to have equal upside potential as company X. I live in a state which treats capital gains no differently than ordinary income.
Aside from having to pay state taxes on $15k, is there any downside to selling company X and buying company Y with the proceeds in order to avoid paying federal taxes on the $15k long-term capital gain?