That being said with all that inflation in the game going on now, there are probably players who have stashed several hundred thousand, if not millions worth of gold away, and in the upcoming Legion expansion, Blizzard will reward players with a lot of gold by giving them a way to spend it all.
For starters there will be a new gold cap set at 10,000,000. There will also be the introduction of a new NPC called the Mad Merchant. Right now he appears to be selling only four items. The first is the Bloodfang Cocoon which is a new spider mount that will cost a whopping 2,000,000 gold. Then there is the Prismatic Bauble priced at 250,000 gold that leaves behind a trail of rainbows whenever the player moves.
This effect lasts 20 seconds and has a cooldown of 20 minutes. Then we also have the Madman’s Luggage which costs 500,000 gold and is basically a 34 slot bag. Last but not least there is the Celestial Calf, a new battle pet that will cost 1,000,000 gold. Obviously a lot of these items will be out of reach for the majority of players, but if you do have more gold than you know what to do with, this could be one way to spend it.