Custom namespace in a delivered Software Component (Version)

If we create a custom namespace in a delivered software component version will it be wiped out if we ever need to refresh/upgrade that same delivered software component version?

For instance, we may need to change a delivered message map in a delivered SWCV.

If we create a custom namespace, copy the MM to the custom namespace, make the changes and subsequently refresh the delivered SWCV, will our custom MM in the custom namespace be wiped out?

thanks,

Rich