As Battle Cat says it is applied following year and extisting contract is applied year you are in. In 'contract screen' if you look at bottom totals for all skaters it should be current salaries for that year but if you move to next year it should be new extented contracts plus existing contract totals of all players signed for future. I believe in 'contract screen' and 'trade screen' is only places you see extended dollar values.
p.s. Cap raises in theory every year I don't know if game calculates extented year cap space with current year cap or with higher values for future year caps?