请教：H1B visit Canada 1 week for Canadian GC landing

When we back to U.S., do we still need visa application? Recalled soemthing like automatic revalidation so if one does not turn in I-94 upon leaving for Canada, a re-entry visa is not necessary. Is it still true?

Also, my wife's H4 will expire in Jan, will that have any impact on our trip in Dec?

 

Thanks!