If your wife's sister files an I-130 immigrant visa petition for her, it will be many years before a visa is available to use. It may be as long as a decade. You can review the Department of State Visa Bulletin for an overview of the wait times. During that time the visitor visas you have issued are unlikely to be impacted, up to the point when the visa may become available in the more near future.
Answered on Jun 25th, 2012 at 4:16 PM