Someone correct me if I am wrong, but this seems that your Pro Tools will continue to work at the version it is right now. But(the big BUT) 2 things will happen:
#1-some plugins may stop working(spelled out in the original deal).
#2-you will stay at the numeric version you now have(to get any new updates after August, you need to pay up to get current).
More to consider; do you need Ultimate? Carbon is supposed to work with Studio, so you might have a less expensive option.