I have transferred my H1b and it's valid up to 2016 but my i-94 is getting expired by Dec 29 2013.
Do I have to apply for I-94 extension?
More information is needed. Its unclear whether you were issued a new I-94. Are you sure that you requested an extension of stay? If so, then a new I-94 should indicate that your stay was extended until 2016. If not, then you may have to get a new visa stamp in your home country.
This will take a bit of preparation, so contact the attorney who filed the petition or consider hiring a competent immigration and visa attorney.
This is general information, not legal advice, and does not create an attorney client relationship.
If your H-1B was "transferred" and valid until 2016, then you I-94 should be valid for the same duration, unless your attorney did not file for an extension of status. Consult with an immigration attorney for additional information.