As a managed WordPress host, WPhost will always keep your WordPress core version and minor security upgrades up-to-date. You can however opt out of major version updates on a site-by-site basis - just open a support ticket.
Any site with major updates disabled will be left out of batch WordPress major core version updates, and will remain on its current major version, only receiving security updates.
Disabling major updates is not necessarily permanent. Sooner or later, any old WordPress version will eventually be deprecated, either by WordPress.org or by WPhost. At that point, sites still on that major version will be updated regardless of this setting for the sake of security and performance. This setting will delay that upgrade by anywhere from weeks to years, but in keeping with WordPress best practice, we won’t leave sites on old versions forever.