6 Months ago, Capcom released the single player demo. Today, people already owning Gears of War, may have noticed the Capcom announcement flier in the box, saying "Check Out Xbox Live Marketplace For New Multiplayer Demo!". For those of you who actually went looking for it, in stead of playing Gears, you might have found out that there is no such demo yet, but to remind you: It has been announced.
Yesterday, Gamespot asked Capcom when it would arrive, they answered pretty vague:
"We will be announcing more details on the multiplayer demo shortly, so please stay tuned."