On my server I really think there are going to be periods when the best selling glyphs will be totally out. Backstab for instance could be the rouge glyph that no one really uses that everyone will be using. So I'll focus on some better bets instead of using the herbs I can get before Tuesday making an even number of everything.
There's no doubt that some glyphs are going to be highly desirable in the coming patch. The issue is most people aren't in the beta and won't know what is good until someone at elitistjerks or wow.com tell them which glyphs to buy. Even then that is a minority. It will take months of testing for people to figure out what glyphs are the "best". In the meantime people are going to just buy them all because they have a boatload of money and it is now a one time purchase.
My plan is to do both ... make as many glyphs as I can before 4.0.1 (I am ignoring minor glyphs fwiw) then watch trade chat for people looking for glyphs that have run out. I have no doubt this is going to happen as like you said ... the demand for some glyphs will have them in a perpetual out of stock state. I'm planning to use that and beancounter to judge what glyphs to focus on post patch.