Hmm, I've no idea what would happen if the Irish bandwagon went into the Euros. I'm sure everyone would enjoy it, though . I was, of course, stereotyping, don't take it personally!
Well I suppose my point is that that figure seems completely unrealistic. 1 billion from where? First, a significant percentage will still watch any high-profile or interesting games. This is true both here in the Republic and in the UK - there are a lot of football addicts. Second, the assumption has been made that the worldwide anglophone audience watches because of England. I feel that that's a bit of a leap. With many of the major players still making it, the competition is still more than high profile enough.
Not that anyone doubts having mad dogs and Englishmen (it's a quote, not aimed at anyone!) at the competition would increase revenue, but as I said, the level quoted seems ridiculous.