Only the queen will survive the winter in cold climates and she may find a nest elsewhere in the Spring. So having closed the entry gap may prevent this from recurring.

If you do notice wasps in the attic next year, it is a far better option to quickly treat the nest directly than poison your home with chemicals that'll blanket the entire attic. There are sprays that look like silly string that you can aim at a nest from a considerable distance (night time is the best time to do this). Also, it is not terribly expensive to get an exterminator to do this, if you are squeamish.

I had someone blast away a nest a few years ago. Took him about 30 seconds and he didn't even bother with safety gear. But since it was up a ladder and I'm terrified of stinging insects, it was worth the $50 to have him do it. Another nest I found attached to the shed I did myself. Results within seconds.