Still, I believe we will see a lot of MARC XML in the future. As an alternative form of MARC, it may be used to display data that continues to be transmitted between libraries in the traditional MARC format.
And let's face it, MARC is not going anywhere anytime soon. The MARC XML schema developed by the Library of Congress will probably coexist with MARC, being used in situations where a more accessible form of the standard is needed.
For a library considering XML, there are advantages to using MARC XML.
The first is that it is backward compatible. Records converted into MARC XML can also be converted back into MARC with relative ease.
Another advantage for libraries using the MARC XML schema is that catalogers will not have to learn anything new. All of the MARC format's tags, subfields, indicators, and byte positions are faithfully reproduced in XML format.
Where one might have added a 246 to the record before, now a field element with a tag attribute whose value is 246 will be added. It is conceivable that the same editors catalogers currently use could be repurposed to read and write MARC XML.