Someone must ask himself what is warcraft 2? What are the basics that are learned from the very essence of the game? I always thought that war2 should be learned from campaigns first (I'm talking about a total newb). You learn relations between buildings and units and their upgrades. Each step is taught one by one. Later in the campaigns you learn to micro-manage your units more, especially catapults. You learn about expanding, resource management, unit management, scouting, and how to defend efficiently from various types of attack.
When you transpose these strategies to online play, GOW is a map that requires ALL of these skills, which are the essence of warcraft 2 IMHO. I agree that GOW is played too much, that there are other maps that are fun and can lead to very complex games. But to say that GOW isn't the future of warcraft2 is to ignore WHY the game is still alive.
I personally have played A LOT on KALI and heat back then, and GOW was the most popular map. About a year ago, i log on ru and still find out that gow/high ef is STILL the most played setup! I didn't enjoy the first games as the players got MUCH better over the years. But you know what? I got a LOT better in no time and I still enjoy learning about advanced tactics on this map as I still get beat up badly by good players.