If you are managing flights for a sporting event it makes sense to hold back the availability in it's entirety for the group stages until you know when each team is going to play.

Then once the games are announced you set nice and high prices in markets with lots of fans for each game and, if you still think that there will be seats unsold, lower prices in other markets.

Tickets for the knockout and final stages can be sold immediately because the market segments for these stages are assumed to be people who actually want to see those later games rather than a specific team.

All that said, there is a lot of talk in the revenue management industry about how you can make a lot of money during major sporting events. That is partly true, but at QR I found that the most value is added because sales and revenue management can reach a consensus on doing things properly, rather than compromising between the sales (price 'em cheap, sell 'em all) and revenue management (go for yield) approaches.

One of my more interesting projects at QR was being project manager of the 2008 PEK Olympics and 2010 JNB FIFA world cup initiatives.

My number one tip

If you have tremendous peace of mind and some flexibility regarding when to travel, wait until perhaps a few weeks before departure to buy your tickets. Every airline will be expensive in advance but when all the fans have their tickets those airlines with weaker revenue management practices will panic and discount heavily because they will realise that they have not sold any seats!

Always happens!

Edited to add

I note that the group stage games have already been announced and that the games will be held in England, which negates some of my arguments above. Most likely BA are finalising their commercial policy and/or waiting for packages to become available and/or negotiating on packages.