As spamrulez posted, season brake made larger when we started to play a world cup in season 4, but to me, World Cup is not the problem, i just think that there ate many unnecesary days without activity, i mean.
Official matches ended on monday, and World cup won't start until friday, we are wasting time there, why don't we start World cup every wednesday? Just accelerating the WC start, we could have a full world cup before january 10th, season could start on jan 11th easily.
The other problem is that preseason is too long! Every new season start on sunday, but the first league match starts 10 days later, why don't we play them on wednesday, 3 days after season change?
Yeah, i know, people wants to invest prize money in new players and prize money is delivered after season change, that should change too, then people would have a bit more than 2 weeks between official matches and the money to do whatever they want. That would also help to keep postseason alive, at least market would be more active (we all know that market will die next week and it won't be active until season chamge).
Some simple changes like these will surely help to keep the game active and attractive, but i am afraid that it's kinda unlikely to see them happening....
