If a new ABN is established, due, for example, to the sale of the sponsoring business, the new company/business will need to be approved as a Standard Business Sponsor under the new ABN. Then a new 482 nomination will need to be lodged linking your visa to the new nomination under that new ABN. Once it is approved you can start working for the new business ABN.
You will need to work on a subclass 482 visa for 3 years in total (which can include working for your initial sponsor whose business has been recently sold and excluding any unpaid leave you may have taken for either sponsor) before you can apply for a permanent visa. Your occupation, however, has to be on the Medium and Long-term Strategic List (MLTSSL)