L1A to H1B during GC processing and I-140 not approved

[SameerT]

Hello,
I am currently on L1A visa (with 5 more years validity left) and my current employer has started GC processing in EB2 category this month. I want to file H1B visa from another employer in April-2018. Since I-140 may not get approved before Oct-2018, what will happen to my GC processing if my H1B gets approved and effective 1-Oct-2018? Would the I-140 still remain valid? Also, what will be the best option for me if I want to get H1B visa from outside?

If my H1B gets approved and my current employer is ready to get it transferred, would my GC processing continue?

Thanks in advance for your help.