I suggest to ask the product owners for a feedback on data retro-compatibility issues.

There are several solutions:
1) drop the old columns, drop the user data
2) keep the old columns (and the user data)
3) drop the old columns, convert the user data to a new sentinel value to be stored in the new column.

Of course, each solution has a different cost in terms of changes to the dbmaint script and the packager script (to communicate / interact with user about such crucial migration behaviors).

In my opinion, such problem should not be addressed in this pull request that already contains a relevant change.