Many years ago I came across a thread which contained a list of all the expansions to be released. This list has been pretty much accurate since 2004. Yes, some of the names are incorrect however the general theme of each expansion is spot on.
According to this list, the next expansion may not be what everybody thinks....
Like it or not, this original leak list has proven credible in the past.
source:
http://us.battle.net/wow/en/forum/topic/7415156004
Here is what I'm talking about, copypasta'd from the above link.
Draenor Set
Azuremyst Isle - 1 to 10
Bloodmyrk Isle - 10 to 20
Eversong Forest - 1 to 10
Quel'thalas - 10 to 20
Hellfire Peninsula - 58 to 62
Zangarmarsh - 60 to 64
Terokkar Forest - 61 to 65
The Deadlands - 63 to 67
Nagrand - 64 to 68
Blade's Edge Mountains - 66 to 70
Netherstorm - 67 to 70
Shadowmoon Valley - 69 to 70
Northrend Set
Borean Tundra - 67 to 70
Howling Fjord - 67 to 70
Dragonblight - 69 to 72
Grizzly Hills - 70 to 73
Crystalsong Forest - 72 to 75
Zul'drak - 73 to 76
Sholazar Basin - 75 to 79
Storm Peaks - 76 to 80
Icecrown Glacier - 78 to 80
Maelstrom Set
Gilneas - 77 to 80
Grim Batol - 78 to 81
Kul Tiras - 79 to 82
Kezan - 81 to 86
Tel Abim - 83 to 85
Zandalar - 84 to 87
Plunder Isle - 86 to 88
The Broken Isles - 87 to 90
The Maelstrom - 89 to 90
Plane Set
Pandaria - 1 to 10
Hiji - 10 to 20
Wolfenhold - 1 to 10
Xorothian Plains - 10 to 20
The Green Lands - 88 to 91
The Dying Paradise - 91 to 94
The Emerald Nightmare - 94 to 97
The Eye of Ysera - 97 to 100
Deephome - 88 to 91
Skywall - 91 to 94
The Abyssal Maw - 94 to 97
The Firelands - 97 to 100
Legion Set
K'aresh - 96 to 99
Argus Meadowlands - 97 to 100
Mac'Aree - 99 to 100
Maw of Oblivion - 100+
The Burning Citadel - 100+++