Not sure if anyone else has posted this since a 'space combat' thread on Slashdot generates so much traffic it seems as if it should crash the servers (Dude, I heard you liked Slashdot....)
Anyway, it's kind of hard to talk about what 'space combat' will look like since 'space' is simply the theater for the conflict to occur in. Its like asking what 'land combat' looks like. When? 2012? 2025? 1942? 550 A.D.?
You probably need to start of with some assumptions concerning your technology. Lasers are a big one. I am not a laser physicist but as I understand it there's certain maximums of focal range that are related to the size of the lens. As I understand it in order to focus a laser at a spot about half a light second away you would need an absolutely gargantuan lens, one so big as to be impractical for combat. Now maybe I am wrong on this but this is an example as to why using lasers over such long distances might not be as easy as some people think.
Of course that assumes we don't find 'loopholes' around the problem such as somehow creating a synthetic lens through spatial warpage or some other technology. On the other hand if you've got some kind of technology that allows spatial warping then you quite possibly have much more effective weapons than photons.
My guess, in shorthand, is that combat in space will bear a certain resemblance to current combat. I suspect you will see guns for a long time (when jets were first becoming widely used by the military a lot of theorists thought that guns were going to go away because of the ranges and speeds jets would be engaging at. You'll notice they are still there because it turns out that at short ranges a missile often isn't the best option). I suspect you will have lots of your 'cheap' units (infantry, drones, spearmen, etc.) backed up with heavier units (tanks, fighter planes, knights on horseback, etc.) often employed along with small numbers of 'heavy hitters' (bombers, battleships, catapults, etc.).
The exact form these all take will be dependent upon the technology of the day.