You must report all your 2016 income on your 2016 tax return. You can't save some for another year. If you fail to report some of your income, the IRS will send a letter requirement payment of the extra tax with interest, if you owe it.
If you don't have your W-2 by February 15 you can call the IRS, they will contact your employer for you.
1-800-829-1040
Or you can use your last pay stub and check the box for "I never got a W-2." This will prepare a substitute W-2 form for your tax return. But if it turns out to be incorrect, you will end up needing to fix it later anyway.
