There is no 3. This game will be Half-Life 2 Episode 2 Part 2. Everyone knows that having 3 in the title would destroy space and time and would lead to a big bang and the start of a new universe.
...we yet realize that America's leadership and prestige depend, not merely upon our unmatched material progress, riches and military strength, but on how we use our power in the interests of world peace and human betterment.
-Dwight D. Eisenhower