Can I change employer with approved I-140 now when Executive action is out

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I'm on EB3 with approved I-140 and recently accepted an offer to move to a new employer who will file my GC in EB2 and port the EB3 date. With Executive action is out to benefit all who have approved I-140 to apply for EAD, not sure moving to new employer who has to file a new PERM/I-140 is still a right option to go for. Does anyone know the timeline when Executive action will be implemented and EAD can be applied? Also, is it possible to backout from already signed offer? My current employer will withdraw once I put the paper and new employer is promised to initiate my GC in 2 - 3 months. Please share your inputs.