In D&D Next, the default core world ought to be the Un-Setting: a Make-your-own-World.
From the very start, the DMG ought to explictly say that each DM is supposed to make their own world.
This should be simply part of the game, as much as character generation.
Explicit directions/guidance:
Clear steps for world-building, as clear as PHB's step for character generation.
Start with adventure-based, gradual building of the setting.
The 5e published modules are supposed to be slapped together on your own wilderness map. Connect dungeons as you go--not ahead of time.
How to make an overland map to connect dungeons. Different cartographic styles from various D&D settings, including earlier iterations.
Later:
How to name a Campaign Setting:
Uses published setting names as examples.
How to make a logo. Shows history of published setting logos.
Two word names:
First Name Element:
Colors: "grey", "black", "red", "blue", "golden", "silver" etc.
Other adjective, usually mysterious: "forgotten", "dark", "savage", "hollow", "known", "unknown", "mystery", "hidden", "secret"
Monster: "dragon", "ghost"
Second Name Element:
Animal: "hawk", "wolf", "eagle", etc.
Geographic: "realms", "moor", "coast", "world", "isles"
Celestial: "sun", "moon", "star", etc.
Arms and Armor: "steel", "lance", "knife" "sword", "axe", "helm", "shield" etc.
Other: "walk", "way", "guard", "watch"
Names like "X of X":
"Council of Wyrms", etc. ("Flight of Dragons", "World of Dungeons", "Dance of Swords")
One word names with two syllables, which already have a meaning: "birthright", "homeward", "underworld", "overlord".
Planet names:
"Earth"-like names: Oerth, Uerth, Aerth, Yarth, Nerath
Other names: Toril, Abeir, Mystara, Aebrynis, Athas
Exotic names, especially for culture-specific worlds:
Mesoamerican: Maztica, etc.
East Asian: Kara-Tur, etc. (give list of Japanese and Chinese name elements)
Middle Eastern: Al-Qadim, etc. (list of relevant Arabic and Persian words)
Only touch on briefly here. More examples in Culture Books.
Also:
The Random Method for world creation:
Randomly roll Campaign Setting name:
If roll existing published setting name, roll again.
How and when to write a Campaign Setting Book:
Explicit sharing of how WotC organizes chapters in Setting Books (past and present).
At WotC website:
How to mimic published settings. How to make it look professional, or at least evocative.
D&D Fonts for download. If WotC doesn't own font, then WotC designers make similar fonts for amateur use. (Like how WotC approved certain alternate Campaign Setting logos for each world's official fansites)
Logo-maker flash utility.
For those who base their world on published D&D Worlds:
How to make a published D&D World your own.
Every self-respecting DM or Gaming Group should have their own name on top of logo: "So-and-So's Forgotten Realms" or "Such-and-such Gaming Group's World of Greyhawk".
Each of these is an alternate timeline of the published world. Other DMs' settings can be reached through the World Serpent Inn.