Travelling Before one week of October 1st - L1b to H1b COS

I am on L1B visa with Employer A right now and my visa is valid till 20-Oct-2013. Employer B has filled my H1B this year and it got approved with COS. Now situation is I need to travel to INDIA urgent for few days. If I travel to INDIA and come back on L1B in USA before October 1st. What could be the scenario? 1) Is there any issues during port of Entry if I return back on L1B just before 2-4 days of October 1st. Can they deny me entry to USA? 2) What happens with my current H1B. Will I be on L1B after October 1st or H1B?