I don't know about soccer, but American sports news is hugely tied up with twitter. It's replaced the sports page of the news paper, ESPN, and even sports radio. I imagine it's the same for international football.

Football Twitter is pretty big, but I don't think it's big enough to cause a big dent.

I can't actually imagine watching NFL without using Twitter during commercials (or after something crazy happens). It's actually quite spectacular

World Cup is definitely going to surge traffic

I would guess so. As long as you are doing business outside North America, this is a fair concern to have.

Twitter experiences massive usage surges every year during the World Cup.

Football fans are a sizable group in pretty much in every social network