Appropriately called 'Glypmas', the 4.0.1 server patch two weeks ago brought in a huge influx of glyph buyers. Some JMTCers pulled in 300k worth of sales in the first few days and others walked off with 50k profits with only a night's worth of preparation.
Now, however, most folks are glyphed out and sales have been declining. But don't switch professions just yet; there's still some potential for profit in the near future.
New Race/Class Combinations - Tauren paladins, gnome priest, dwarfen shamans--all of these new rerollers will be needing glyphs. The first trio of glyph slots is level 25; those who are seasoned rerollers will be there in less than three hours. Within a week many will have hit 50 for the second trio of glyph slots.
Ink Trading - Once Cata releases, the ink trader will be updated to trade down Cata inks rather than Ink of the Sea. With the number of rerollers there will likely be an abundance of lower-level herbs to start but the mid-tier and Outland herbs will be in less supply.
New Goblins and Worgen - New characters mean new glyphs. Those gunning for server first will be at 25 within a few hours (server stability aside) and 75 within a few days. Everyone else will be hitting 50 within a week and 75 within two or three.
"Skills to Pay the Bills" - This new achievement will hopefully bring in some extra draw for those glyphs that no one really knows what to do with. Each class has roughly 30 glyphs available so expect a number of folks to figure 'might as well get them all!'.
How do you plan to prepare?