Upon sale, you will have depreciation recapture whether you took it or not. The IRS will assume you took it, and even if you didn't, you will need to pay it back.
Your two options right now are to go back and amend (for the years still eligible), or, better, IMO, just do catch up depreciation this year to bring you up to where you should be.
If you don't have enough taxable income right now though, it may not be beneficial. Consult a tax professional.