There is an advantage with concurrent filing which is you are in AOS pending status till either your I-140 is denied (for whatever reason) or is approved and you get your AOS approved too. So to answer your question, even if your I-140 is not approved, because your PD is current you were eligible for AOS filing and once filed you are in AOS pending status. So if your L1A EOS is denied for some reason you will still be in a legal status.
Is it the same employer?
As such H1B & L1 are different applications and can be processed in parallel. Even if you submit your H1B documents, L1A via PP may be approved before H1B and so you will be in L1 status before your COS to H1B is approved.
You should only apply for H1B if you are ok switching to H1B from L1 if the H1B COS gets approved.
Check with your company attorney if the above will not create any issue with your AOS application if you change from L1A to H1B as your AOS is applied under EB1 based on L1A.
If I were you, I would wait for L1A EOS and the AOS processing. If your L1A was approved earlier, your EOS application should be approved and you also have high chances for AOS approval.
You should immediately apply for PP for your pending L1A EOS application.