Also Delta terminal 2 gates are known as the "C" gates. The T4B gates are now the" B" gates.
There will no "A", "B" or "C" letters added to the gates. I believe you see them as a *passenger* when walking inside of a terminal, and you will seem indicated with a letter on a terminal map on a website, which is supposed to be used by passengers, but according to the official Jeppesen charts of March 2013 (used by pilots, which is what you are as a sim user), there are no letters, and gates at Terminal 2 are 20 to 22, 23A to 23K, 25L, 25M to 25S, 26, and 27 thru 29.
Same for Terminal 4: the only one officially labeled with a letter are 2A/2B, 20A/20B and 25A/25B, and these are all parkings too close to each other to be possibly represented in the AFCAD.
Of course, we might use the GSX custom naming/grouping feature, to logically group them better, for example having two "Councourse A" and "Councourse B" for Terminal 4 in the GSX selection menu, but that's just a convenience feature, won't change how the scenery or the AFCAD needs to be done.
Of course, if you have more updated information from actual piloting charts, feel free to refer to the source.