EB2 to EB3 porting , is EB2 still valid ?

[BABUK]

I'am porting my current employer's EB2 to new employer's EB3 . In case if I want to come back to my current employer EB2 in future  and process my green card ,is there any change in EB2 priority date with current employer  ? or is current employer's EB2 still valid? . 

Tnx,

SK.