Yes.
Cohorts in Mixpanel are dynamic: every time you use a cohort in a query, Mixpanel recomputes who is in it “as of right now,” rather than using a static snapshot. [How cohorts are computed]
When you create a cohort from an Insights report (via “View Users” → save as cohort), that cohort’s definition is based on the same behavioral/property conditions you used. As new visitors later perform the event(s) that match those conditions, they will automatically be included the next time the cohort is evaluated or used in analysis. [Cohorts; View Users]