That is a very good question. As you might know Belgium is a nation with two official languages, and so there are two channels that will broadcast from the World Cup. One of the channels is RTBF and the other channel is VRT. You will for sure be able to watch at least one of these in your hotel room, so that should be no problem. If not, just leave the hotel and find a pub and drink so Belgian beer, and you will be able to watch the matches all across Brussels.
If you would rather watch the FIFA 2014 World Cup online, then you can do so either at the websites of the TV channels. You will need a Belgian IP address to watch those streams, but if you prefer an English commentator, then you can watch the World Cup online on both ITV and BBC in the UK using a VPN provider. Read more about watching the World Cup online on ITV and BBC from abroad in the linked articles.
And if you have some spartetime in between the different matches, why not join in on a Brussels Beer Tour?
By the way, Belgium will play against Algerie on June 17th, face Russia on June 22nd and then South Korea on June 26th. Hopefully that will not be the last match for Belgium during the World Cup. For further schedule, visit watchworldcup.net.