Attack with what? With weapon systems that do not need any particular position except 'be in range', and if these weapons are rendered useless what do you need to get into 'optimal position' with?
I think directed energy weapons would be filling that role IMO as I said, for a number of reasons, but also this one of yours - attack with what?!. I do agree with you regarding the gun in terms of a slug/projectile throwing weapon - and I don't think railguns will have the rate of fire or capacity to fit on a fighter either, not before DE weapons will at least. I think everyone is in agreement that maned fighter aircraft are ticking down to being gone, or at least be very limited.
Unmanned fighters will still have to fight other fighters, manned or otherwise, in order to get control of the airspace in any future conflict, especially vs peer nations that have close or the same level of tech and equal or more numbers than the USA/NATO. And, if the trend continues that defensive ECM systems will eventually trump most offensive radar and IR guided weapons, what else is there other than direct energy or guns of some other type, with which to kill the other aircraft.
I will say though that the manned/unmanned argument could be similar to the whole "no gun" argument prior to Vietnam, and things won't work out the way many thought, and manned aircraft MAY be around for longer than anticipated. Who knows. Everyone and their dog was convinced a gun wouldn't be required, and while missiles according to the kill graphs in that CSBA paper have killed the majority of fighters in a2a combat since the 70s, the gun still did get kills, and with the Israelis quite a number of them. I guess that since the CSBA article is making the case that the gun isn't nearly as important as missiles again, that if you take that, and then remove the missile lethality due to modern ECM systems, like Predator is saying, then what? IMO it'll have to be an energy weapon, or something else completely new that can't be jammed, spoofed, or kept out of range from.