Why is it a surprise that Gears 2 will be out in November? By then it will have been 2 years since Gears, Epic would most definately have been working on the sequel pretty much as soon as Gears 1 was finished. The first game in a series will generally take longer to develop, sequels will typically need less time in development (especially when they are just a continuation of the story).
Infinity Ward started working on CoD4 as soon as they were done with CoD2, that would make it a very similar timeframe as seen between Gears 1 and 2. An example of a series taking slightly longer between sequels would be Halo, as each time they had to build the game from the ground up. That's not necessary with Gears 2, which is why we see a slightly shorter development time.
Yeah, it isn't unreasonable for it to come out now. another example is (i know i know) Insomniac. They had R:FOM out same time as GoW, they have released a full game and they plan to have R2 out in November. So it isn't unreasonable.