Overall, pretty much every zone has at least one new flight path. With a few exceptions, the plan is for you to spend five levels in each zone. You'll typically have 2-4 choices for any given level range. In most cases, you can move on to the next zone a level early - if you find yourself several levels ahead of the curve as you finish an area, you can probably run a dungeon or two with the dungeon finder and then skip a zone to move on to the next five level tier. Here's the rundown, based in part on the list of Horde and Alliance breadcrumb quests.
Alliance: Westfall/Redridge (humans), Darkshore (NE and Worgen), Loch Modan (Dwarves, Gnomes), and Bloodmyst (Draenei, presumably unchanged from TBC)
Horde: North Barrens (Orcs, Trolls, Tauren), Azshara (Goblins), Silverpine (Undead), and Ghostlands (Blood Elves, presumably unchanged from TBC)
The quirk with this level range is that you might be starting as early as level 9 (if you ditch the newbie zone the moment you qualify for the breadcrumb quest) or as late as level 13 (which I hit on some characters with rest exp, heirlooms, and exp for harvesting). I find it interesting that the six non-TBC zones got some of the biggest and most dramatic geographic revisions of the Cataclysm. Perhaps Blizzard decided that they had to show veterans changes early and often if they want them to stick with new alts to level 20?
Ashenvale (both factions), Wetlands (Alliance), Duskwood (Alliance), Hillsbrad (Horde)
Though these zones are considered "contested" territory on PVP servers, the contest has been won in all but Ashenvale; the remaining three zones only offer quests for the closest side. (From here on out, everyone shares all the zones.) It's kind of unfortunate that the Horde bottlenecks into literally two choices so early in the level progression.
I've actually done Duskwood on an old Discipline Priest alt. All of the major plots from 2004 remain in the zone, they've just moved so that you don't have to run back and forth across the zone repeatedly.
Stonetalon, Arathi, and North Stranglethorn Vale
I'm kind of looking forward to NSTV because I hear that there are quests in the former raid area of Zul'Gurub. Otherwise, I can't say that any of these really interest me.
Desolace, Hinterlands, South Barrens, Cape of Stranglethorn (South STV)
This is the only range between 20-60 with four zone - more on this below. The Alliance breadcrumb quest for South Barrens is a bit weird, in that there's no flight path or boat - you have to run/swim from either Ratchet or Theramore. You'd think they could have chartered something for the occasion, given that the NPC is standing on what appears to be a dock.
Ferelas, West Plaguelands, Dustwallow
WPL was just about the first place I went to visit when 4.03 went live. The geography has not changed, but the zone has a completely re-written plot, many areas that are no longer plagued, and a variety of solo quests pitting players against the bosses of the Scholomance instance.
Thousand Needles, East Plaguelands
Here's another unfortunate level range with only two options. Worse, IMO one of the options is way better than the other.
The Scourge-mopup operation in EPL is not as far along as the effort in WPL, so the zone looks very similar to how it did previously. Also, this area probably holds the record for most flight paths in a single zone, since ALL of the former world PVP towers get their own neutral flight points.
Meanwhile, TN was once a canyon and is now completely underwater. Can't say this is going to be a very hard choice.
Tanaris, Felwood, Badlands (45-47) + Searing Gorge (47-50)
Blizzard opted to deal with some of the sparser zones of the Central Eastern Kingdoms by having them span narrower level ranges. The Badlands is supposedly amusing.
Un'goro, Winterspring, Burning Steppes (50-52) + Swamp of Sorrows (52-55)
This is another range that I'm just not that excited to see. The geography is pretty much the same as it was, and there aren't any major changes in the balance of power (like, say, the Forsaken conquering Southshore).
Levels 55-60 (or 58)
Silithus, Blasted Lands
There's only two options here, but you do have the option of moving on to Outland and the unchanged TBC content at 58 if you don't hate that entire expansion. Also, you now get hit with a 90% exp penalty for mob kills once you exceed that expansion's level cap (60 in this case), and you can unlock flying mounts (usable in Azeroth if you have the Cataclysm expansion - note that everything else in this post is 100% available to players who do not own Cataclysm).
I'm definitely more interested in the Blasted Lands, which got bumped up by 10 levels (while WPL and EPL got bumped down with the demise of Arthas) so that players can actually be standing at the Dark Portal when they reach the appropriate level.
A math error at Blizzard?
Loosely speaking, you're looking at two core paths that get you from level 25-60 using roughly adjacent zones:
- Kalimdor: Stonetalon, Desolace, Ferelas, Thousand Needles, Tanaris, Ungoro, Silithus
- Eastern Kingdoms: Arathi, Hinterlands, WPL, EPL, Badlands, Searing Gorge, Burning Steppes, Swamp of Sorrows, Blasted Lands
There are also three little detours:
North+South STV (25-35)
South Barrens+Dustwallow (30-40)
Looking at it that way, I wonder if Blizzard screwed up the level ranges on South Barrens and Dustwallow; if these zones had instead run from 35-45, there'd be a complete third path from 25-55. Now, there is instead an inexplicable glut of content from 30-35 and a painful gap from 40-45. I suppose that you can make up the difference with the dungeon finder (or do the two STV's and then run all of South Barrens and Dustwallow over-level).
One final note, Wowhead says there are about 2900 quests from levels 20 to 60, and about 900 of those are available to both factions (i.e. neutral questgivers). This does not account for situations where the two factions have the same quest with different flavor text (and does catch some of the early TBC quests), but it gives you some idea of how much duplication you're going to see if you're playing all the paths on both sides.
So, how many leveling paths are there in the old world revamp?
12 paths to level 5 (2 unchanged from TBC)
10 paths to level 10 (2 unchanged from TBC)
8 paths to level 20 (2 unchanged from TBC)
5 paths to level 25
3-6 paths to level 55 (depending on how you're counting neutral quests)
2-4 paths from 55 to TBC
The odds that I'm going to end up with four new level 60's by the end of Cataclysm aren't great, but I suppose they're not zero either.