Blizzard has an interesting challenge on its hands for the game design of StarCraft II. On one hand, the original has proven to be one of the most popular and long running multiplayer videogames of all time: not only is it still played today, but it's an institution in South Korea, where the game's popularity and its level of coverage essentially make it a national sport. On the other hand - and against this weight of expectation for a balanced, deep game that will thrive in the pro circuits - Blizzard is also looking for a blockbuster hit: a game that will go beyond the hardcore and enter the mainstream.
Of course, the company has proven time and again that it has what it takes to do just that, and that making a game that will appeal to the hardcore, as well as be accessible for mainstream players is not a diametrically opposed challenge, but part of the same process. Indeed, strangely enough, mainstream appeal is born out of making a game for the hardcore.