I see no mention of the SQL 7.0 exams in the "Exams Scheduled for Discontinuation" page on the MS Web site. According to recent policy statements, this means that the SQL 7.0 exams should remain active for at least another 12 months. Also, given MS's recent decision to put version designations in place for its certifications, the MCDBA won't "go away" it will be designated as "MCDBA for SQL Server 7.0" and thereby indicate its vintage. I think this credential is safe for at least another year, probably longer.
This was first published in October 2001