Mike Austin is still teaching.
Being a TGMer, and having taken lessons from Mr. Austin last year, I have also noticed similarities between TGM and "Austinology:"
1) Both stress the connection between the upper left arm and the upper left chest as part of the downswing. In TGM, this is referred to as PP4/Pressure point #4; Austin calls this move the Figure 7--one line is the shoulder line, the other line is the left arm.
2) Both stress tilting to get on plane. Austin says he "crimps his right side on the downswing." That is, you shorten/lower your right side and raise/lengthen your left side. He talks about directing his "bottomright rib into his right hip." These are his words.
3) Both talk about the importance of creating the angle in the right elbow during the backswing (Austin calls it "flexing your right elbow," Homer Kelley calls it Accumulator #1), and maintaining it as you tilt during the downswing. On some other boards (specifically, Single Axis Golf), I've seen people interpret the throwing action Mike Dunaway describes in the "Secrets of the Game's Longest Hitter" (or whatever the video produced by Peace River Golf is called) as releasing or straightening the right arm/elbow from the top of the backswing. This is wrong. During my lesson, Mike Austin told me to tilt then throw--that is, you tilt your spine until you get on plane, then you straighten your right arm.
I am sure there are other similarities that are unique to both TGM and Austinology, but I can't think of them right now. I would like to note one major difference: TGM teaches that the left arm/hand rolls to square the clubface, then the left arm rolls/swivels the club to get back on plane from separation to followthrough. And that from release to followthrough, the left wrist is to remain flat. Austin believes that left arm DOES NOT roll or swivel, because if you roll your left arm, you'll hook it. In the move he teaches, the left wrist bends after impact to keep the club on plane, causing your forearms to touch during the followthrough. Basically, it's a very angled--almost vertical--hinge that keeps the clubface parallel to the spine or perpendicular to the ground when your arms are parallel to the ground during your followthrough. Another way to think of it is that in TGM, whether using angled or horizontal hinging, PP3 will roll (in varying degrees) on top of the grip during the followthrough; during the Austin followthrough, PP3 will stay behind the grip, and your thumbs will stay on top of the grip, causing your left wrist to bend and your forearms to touch.
It's been a while since I've thought about this stuff, so I probably am not 100% correct in my representations of TGM and Austinology, but I think that I've depicted them decently enough.