Presumably your wife's approval will have a start date of October 1, 2013. You indicated when her work permit expires, but not when her L2 expires. You should speak with the lawyer who filed the H1b to see if you request a change of status, and what the start date is supposed to be. L2 dependent has some advantages over H1b, in that you can change employers and the employers do not need to file any applications with USCIS. However someday if you ever need it, the H1b will let you become an H4.
The above is intended only as general information, and does not constitute legal advice. You must speak with an attorney to discuss your individual case.
The only way a change of status to H-1B can legally be made is if the applicant is in some other valid status through at least September 30th.
Your employer needs to retain an experienced immigration lawyer to review all the facts, advise them, and handle the case. Your employer can find one through http://www.ailalawyer.com.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.