The reason that viruses spread more in cold weather is because people crowd together in small, warm indoor spaces, then take their germs to new small, warm indoor spaces. So if there's a break in that chain, yes, it will slow down spread.

But influenza is contagious for 24 hours before symptoms and 5-7 days after symptoms start, so it's going to depend on how long people really stayed home and what they do immediately after. A week is probably going to cause a small dip but nothing lasting.