I agree that the future is open and that everything is possible. However, from our past history and evolution, we can try to guess how it will probably be like.
Take a look at how the fighters evolved since WWI: always bigger, heavier, faster. Compare a Sopwith Camel in size and weight with a P51, than compare this P51 with a F15...
Range of weapons and sensors has increased dramatically too.
Saying that combat spaceship will be small and will fight at short distances is one of the less probable hypothesis. It would be much safer to stay in a big ship at extreme range and launch unmanned smart drones which will do the dirty work and take all the risks (besides, unmanned vehicles would be able to withstand much higher acceleration than manned fighters).
There is one constant tho: man's imagination to make life miserable to other men is infinite.
As usual, edited for typos and weird use of Shakespeare's tongue