As the 4th ed players are raging over the warlord this is not the 1st time classes have been excluded from the game. I was not around for the 1st ed to 2nd ed transfer so I'm not sure if the Monk and Assassin being excluded created any major friction. I went from BECM straight to 2nd ed and the classes were later added back into 2nd ed although the assassin became a kit.
Whatever problems 3rd ed had it made all of the 1st and 2nd ed core classes appear on release. So far it is the only version of D&D to have the Barbarian as a core class. 4th ed did eliminate classes but that may not have bene the only problem more the scale of it IDK as they nuked 5/11 3.5 classes and several races a s well which had been in the game since 1st ed such as the Gnome.
Anyway to me core is fighter, rogue, wizard and cleric but even then only if you would be selling D&DN as a reboot of the franchise. The Paladin and Ranger have been in all ediitons and 4th ed cut the Druid an Bard both of which had been in 1st-3rd ed. So I regard those as core classes as well (outside a reboot/BECM clone). So that leaves 8 classes that if I was designing D&D any edition I would not cut at all short of selling it as a reboot.
That leaves the Barbarian, Monk and Sorcerer which have only been core in 1 edition or 2 in the Monks case. Cutting classes is always going to be an emotional thing but hypothetically if 4th ed had not have cut them or had maybe only cut 1-2 classes instead of 5 would it have mattered? If each edition keeps adding more classes to the game how many classes do we really need in a core book? 11, 13 15 20+? Will 7th edition try to include 13 classes+DDN and 6th eds classes? The more bloat the more likely they will do a reboot back to 4 classes one day IMHO.
Or do we freeze the core classes at a point in time (1st-4th ed pick one) and rotate a few in and out every edition. 13 classes is getting towards the upper limit for me in terms of how many classes you need or want in a core priduct, 15 being the absolute most I would probably want with a preference for 8-10 classes and I am currently using 10 (3.5 ones minus sorcerer, mostly becuase current rules I am using lack the Sorcerer class). If the developers decide to cut a class for whatever reason maybe they need to ask the fans so to speak about it even if it is something like "Hey guys we're having problems with the assassin because of the evil alignment things and its resemblence to the Rogue, we are planning on releasing it later in a splat".
So basically how do you cut a class, do you want to cut a class and should they ask to cut a class?