Will my status change to H1B (cap-approved) from F1 on Oct 1? My F1 and I-20 expires only after this year. I want to continue to be in F1 till 2014.

October 1st is usually the date put on I-129 petitions where cap H-1B petitions are filed. As such, your F-1 status would automatically change to H-1B on that date if it was approved and that date was requested. Your alternative if you do not wish to change status to H-1B is to have your potential employer cancel your H-1B approval prior to October 1. 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.

If you have applied for a change of status and the new I-94 card has been issued, then you are already in your new status.  If you want to be in F1 status, why did you apply for H1B status?