Correct, the photos will remain attached to the entries as mentioned in my reply on the other thread.
It is always advisable to create a database backup first so it is easy to roll back in case of a unforeseen error. Also, to do a test import of 5 to 10 entries to make sure the results are as what your are expecting them to be. These are cautions I follow when doing imports and updates in bulk.
Hope that thoroughly answers your question!