Let's use a Forsaken for our example, since they have no factors working against them like racial boundries on mounts. Keep in mind that some races will have a harder time, like Tauren can't use two of the five Horde mounts, and Gnomes don't allow anybody but Gnomes and Dwarves to use mechachickens.
The Horde has Peacocks, Raptors, Wolves, Skeletal Horses, and Kodo. From a glance at Wowhead, there seems to be...
- Seven Hawkstriders
- Five Skeletal Horses
- Six Raptors
- Six Wolves
- Five Kodo
Then there's the basic PvP mounts, the Black War Whatevers. There's one of those for each race, so that's 34. Then the Alterac Valley mount from Marks of Honor, so we're at 35. Of course, the PvP mounts each require 30 Marks from Arathi Basin, Alterac Valley, and Warsong Gulch. This comes to a total of 150 Marks for these mounts, plus some extras from AV for that one.
Everyone loves flying mounts, and there's tons of those.
- Seven Wyverns
- Six Nether Drakes
- One Hippogryph
- Five Nether Rays
I forgot Talbuks when we were looking at ground mounts. There are 8 Talbuks from Reputation (Exalted with your Nagrand buddies), and 2 from Halaa, a total of ten. Roughly 600 more gold, some time spend grinding rep, some time spent PvPing, and we're up to 64 mounts.
We're running a little dry on things that are easily accessible, so let's get into the rarer mounts.
There are four flavors of Qiraji Resonating Crystals in AQ40, which you can get just by killing random things. They drop very frequently, and the stuf in there is trivial at level 70 (even easier at 80), so we'll count it. 68 mounts. Edit: The devs have stated that these will not count, so my numbers are a little off. Just subtract four.
Brewfest has special holiday mounts, in epic and vanilla forms. We're up to 70 mounts. If you were lucky and picked up the rams last year you have an extra 2, but we'll pretend that never happened.
Hallow's End has mounts, but last we knew, those expire and probably won't be permanent mounts going toward this total. We're still at 70.
Early adopters of the epic mount may have the old school, unarmored versions of the epic mounts, so they have an advantage. For discussions purposes, we'll pass over those, since you can't get them anymore.
There are the rare drop/challenge mounts:
- Baron Rivendare's Deathcharger
- Swift Razzashi Raptor
- Amani War Bear
- Zulian Tiger
- Reins of the Raven Lord
- Fiery Warhorse from Attumen
So adding all of that up, is it possible? Yes, but it isn't going to be fast, easy, or cheap. It will take a lot of time and a lot of gold. Until Wrath of the Lich King anyway, then it becomes easy. You probably won't have it at level 70 when patch 3.0.2 launches, but you'll definitely be able to get it by 80 when a whole slew of new mounts are added.
Tauren are at a disadvantage right now, while Engineers, Gnomes and Dwarves have an advantage. Those differences won't be a big deal once Wrath hits, but they're there nonetheless. It'll be a hard road, but at least you'll get other achievements on the way, right?