I have submitted my i539 form on 3rd of Nov but not received the receipt yet. My i94 is expiring on December. I am legal to stay post dec?

At this time, USCIS has given notice that its issuance of receipts is delayed. You can continue to stay legally in the US so long as the application is ultimately receipted and not rejected by the Service. In the event that it is rejected, you may wish to correct the error and send the application back in as soon as possible with a request to USCIS to forgive the late filing (See form instructions for late filings). Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.