Here is all that is there in USCIS and DHS memos about people with approved I-140 who cannot file I-485 due to visa numbers not being current: "Specifically, USCIS should consider amending its regulations to ensure that approved, long-standing visa petitions remain valid in certain cases where they seek to change jobs or employers." (DHS policy memo, emphasis added) "USCIS will: What -Provide clarity on adjustment portability to remove unnecessary restrictions on natural career progression and general job mobility to provide relief to workers facing lengthy adjustment delays. When-Upon issuing necessary guidance and regulations." As I read it, the DHS language is rather restrictive - the visa-petition (I-140) has to be "long-standing", then "in certain cases" it will remain valid (no need to refile perm and I-140).The USCIS language is rather vague and could be read more broadly. Bottomline - wait till rules are published for comment unless USCIS provides some guidance before then.... There is nothing about pre-registration anywhere in the documents - either those released by WH or the DHS/USCIS.