I don't intend to work on this myself right now :-/, just letting this be trackable somewhere.
Views D7 exposes Field API fields using table aliases that are different from the ones exposed by CCK D6 ('node_data_*', didn't make any sense in D7). --> D6 views will lose their fields in D7.
Views D7 provides a mechanism to dynamically translate old table aliases into new ones ('moved to' property in hook_views_data()).
Exposing those 'moved to' information probably belongs to content_migrate rather than Views module. Cannot be part of content_migrate itself, since the module intended to be uninstalled once D6 fields are migrated.
Possible approach :
- content_migrate sets a $field['d6'] = TRUE property on migrated fields (Field API will preserve this through field_update_field() calls)
- a small dedicated content_views_compatibility (or something) side module just implements hook_views_data() and exposes the 'moved to' data for the old aliases, for each field having $field['d6'] set.
Granted, we won't be able to magically make every D6 views work perfectly in D7 (field formatters, settings for some handlers might have changed...), but at least people wouldn't be obliged to remove old fields, filters, args, re-add new ones, just adjust existing ones.