Mother Nature took care of your Late Blight problem when freezing weather arrived. Late Blight cannot survive freezing.
Your soil is not contaminated. Late Blight needs to have living tomato or potato plants to survive. It doesn't live in the soil and it can't come back from the soil next year unless there are infected potato tubers there that won't get frozen. Freezing the potato tubers kills the tubers and the Late Blight that is on them.
Any Late Blight that shows up next year will be carried in to your garden on the wind as tiny spores from somewhere else, most likely from someone else's infected potatoes or, as happened in 2009, from infected tomato seedlings shipped in from a warmer climate. It won't come from your soil.
Here are a couple of FAQ's that may be helpful:
http://northeastipm.org/newsandrepor...ateBlight.html
See question #18 here:
http://www.hort.cornell.edu/departme...path/lbfaq.pdf