It's an interesting question. IMO, one of WoW's biggest accomplishments relative to the few other MMO's I've dabbled in is to have established a pretty stable economy. Gold is always worth something ... they manage to keep the right balance of how much money you can earn vs. consumably items you NEED to buy on a frequent basis vs. repair bills and so on. They throw in the 5k gold flying costs that a) make those things feel like more of an accomplishment but b) suck gold out of the economy, preventing rampant inflation. Which is especially impressive given that there are gold farmers and the people who buy from them just pouring currency into the economy.
Having said that, there definitely is some inflation in the game. Knocking out 10 dailies in an hour and getting 100-150 gold is really no problem. Grays off mobs are a few gold apiece.
I suspect that prices will be crazy the first few weeks after Cata goes live. There will be rare BoEs ... either because they're drops or because only a few crafters have gotten the recipe and mats to craft them, and so on. Those lucky few who get those things will be able to charge exorbitant prices because there are, no doubt, "rich" players who are willing to buy their way to BiS goodies as early as possible. (unfortunately, a lot of those "rich" players probably paid $ for their gold). The last few months, prices for iLevel 264 BoEs has been 5-10k apiece, and in some cases higher (although such transactions dropped bigtime after 4.0.1). I wouldn't be surprised at all to see BiS BoE items to go on the AH for 10-20K or more initially. With that, you almost need an unlimited pocketbook. But I doubt many people see having 100k gold as their primary gearing strategy.
IMO ... the game is easier when you always have 1k+ gold on hand. While on one hand, it's less rewarding when you spend it because you havent' had to work for it(I remember the thrill of getting my initial lvl 40 mount ... which cost, what, 100g ... after 4.0.1. I paid 5k for flying master and it was about as exciting as buying the next level of Gift of the Wild). But that much gives you the ability to generally do what you need to do. More than that is really a playing strategy ... investing in a cash balance rather than, say, rep or justice points or whatever.