There is no reason to delay your tax return filing while waiting for your employer to complete the correction. Unless you have multiple employers resulting in your total wages exceeding the $128,700 Social Security wage base for 2018 or your income is high enough to make you subject to Additional Medicare Tax (Form 8959), the amount of Social Security and Medicare taxes shown on your W-2s has no effect on your income tax return. Just enter the W-2 as corrected. There is a chance that entry will be questioned if the employer has not filed the W-2C, so if requested you might have to supply the paper copies of the W-2 and W-2C.
