Yes, you can make gold from the regular updates and maintenance schedule that Blizzard goes through. It is only a matter of being fully aware of the market and the effects of Blizzard's actions on that market.
A great way to make money is to pay close attention to the logon menu when you first login. Located in your display menu, where they inform you of the latest patch, their next maintenance closure and any other Realm news, you'll find the necessary clues. Usually they give you 2 or 3 days to prepare for a maintenance reboot so that players have time to be ready. The first thing you need to do when this happens is to wait until before the reboot and then start bidding very low on all items that are ending soon or in a short while.
When the servers go offline, you will be the high bidder because the servers are offline and auction house is obviously not being used and no one else can bid. You will win a lot of good items for cheap and then can resell them for their actual value and make a decent profit. Another great thing about server maintenance is that all of the limited supply items are back for sale at all of the vendors. If you can quickly reach those vendors and purchase them first, you can make even more money by hoarding the limited supply goods. Good places to find these vendors are Ratchet, Gadgetzan and Booty Bay.
Patches and Upgrades
World of Warcraft always releases the patch notes for the newest patches a little before hand, giving you time to see what things will be changed when the next patch goes live. The most important thing to look for are the items that are being altered, either with stat changes or drop percentage decreases. Now, before the patch is released, starting farming for these items in earnest. When the patch is released, supply and demand dictates that you have the market cornered and can sell the items you just farmed for a little more gold than before, especially right away. If, however, you notice that an item is going to increase its drop rate, ensure that you get rid of any that you are still holding on to before the price plummets in the auction house due to over supply. This is just a nice way to gain a little inside information before each new patch and be prepared for what comes next.