If your status is changed to H-1B effective October 1, 2012, then you will get a new I-94 that indicates your new H-1B status and the date of its expiration. If you do not leave the U.S. then you don't need an H-1B visa stamp in your passport, because the only time you need one is when you are asking to enter the U.S.
If you do need to go outside the U.S., then you will need to apply for an H-1B visa stamp in order to return to the U.S.
Your company's immigration lawyer should be answering these questions.
If you are uncomfortable with him/her, or if (heaven forbid) the company doesn't have an immigration lawyer, I suggest that you pay for a consultation fee with someone ... my firm, and most other attorneys on Avvo will be happy to assist.
First, if the H-1B papers haven't already been filed, and if you are not in a CAP-exempt occupation ... there is no way that you will have an H visa approved for October 2012 .... we ran out of visas a few months ago. The next batch won't be ready until October 2013 ... with pre-filing not being allowed before April 2013.
Assuming that your company filed before we ran out of H visas, and were saving money by not doing Premium Processing, you will get a new I-94 in the mail, with a start date of October 2012 ... at that point your H-1B I-94 will no longer be good.
Yes, you can use the new H-1 I-94 to work .... but not travel.
Also you can NOT use the old L-1 visa stamp to travel ... you will need to apply at the US Consul the next time you exit the US.
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FORMER IMMIGRATION LAW PROFESSOR -- LEGAL DISCLAIMER: This answer is offered for informational purposes only. It does not constitute an attorney-client relationship.
If USCIS changes your status, they will do so effective October 1, 2012. As of the date USCIS changes your status, you are no longer in L-1. Any trips outside the US after your status is changed will require that you have an H-1B visa stamp in your passport in order to return to the US.
You should retain an experienced immigration lawyer, whether myself or one of my colleagues, to review all the facts, advise you, and handle the case.
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.