Inscription was my main gold-making activity during Wrath, earning me hundreds of thousands of gold. When the glyph system was changed, making them learn-once-and-use-them-forever items, I thought that the market might dry up. I know that a lot of scribes got out of the glyph business at that time.
To an extent the market has gone south, as predicted. I sell less than 1/3 the volume of the glyphs that I did during the Wrath days.
However, Outland and Northrend herbs are pretty scarce on the auction house because there are not a lot of players leveling and herbing in those zones. That drives the cost of Ink of the Sea and Ethereal Ink up. At the moment I am buying stacks of Outland herbs for 60g each and then selling glyphs made from Ethereal Ink for around 200 gold apiece. Even if I only sell a handful, it still earns me a lot of profit.
Eventually, the cost of Cataclysm herbs will come down. When that happens the older inks will be bought from Jessica Sellers in Dalaran in exchange for Blackfallow Inks. Until that happens, inscription is still quite profitable.