This is the only game ppl cant wait more than a month without complain.
The others take 3+, and most fighters dont get extra character at all.
They need to make the char design, the animation moveset, special moves, balances, dialogues, history and cutscenes, costume, intro outro, char icon, background from 0, now take all this hardwork and multiply by 2(or 4 like you said).
Sounds easy? Grab your Photoshop/coreldraw and try to replicate a simple background of one character, to see how much time its gonna take.