The problems I see with the Typhoon as a replacement is due to the size difference. The Hawk is a small aircraft, allowing them to fly very tight, very close to each other. The Typhoons are a lot bigger and have a bigger wingspan which would make some formations a lot wider than the Hawks can do. I also doubt if they could get the Typhoons just as close to each other as the current T1s are able to.
Though the Hawks don't need replaced until 2020. Some have suggested the Tucano, but I don't see it as they have a replacement date of around 2020 too.