Lack of skilled IT workforce, but they do not raise wages
The factual observations you've listed fit neatly with the law of supply.  You've seen that wages (price) have fallen, and during the same period, supply has gone down.

The fact that companies publicly complain that there aren't lots of cheap, highly skilled workers available is not the same as companies being willing to convert that into effective demand by raising wages.

One common reason companies moan about things publicly, for instance, is that they want the government to intervene to help them.  In this case, perhaps they want government to provide more subsidised IT training, or permit more immigration in the sector, either of which could lower wages further or prevent them from rising.