Well... you'll be able to power your professions to 525 in Cataclysm.
Which allows more of the same, from the get-go, to continue the gold accumulation.

Gold lets you buy things, pretty simple.
When a new raid zone comes out, there will be BoE's and you can be amongst the first to have them.
Same idea with Battered Hilts or any other BoE.
Ditto on recipes, except those are also an investment since you will make a profit off of many combines.

I know on my server, there are a lot of highly rated (arena) players, who will sell rating.
You can get a toon to 1800, in 2's for 3-4k in an evening.
If you've been losing (trying to win) in 5's for several weeks, that's an immediate huge weapon upgrade.
Gold opens a lot of doors.