A few days ago the engine and definitions updates were corrected after several problems. The QA procedures were also improved, and avast 7 is in alpha development (soon to be beta). My guess is that the engine is under some tests and adjustments, and that the developers are focused on avast 7.
Just as the scanning speed got improvements during the last year (using engine updates), we will probably see improvements again. If not, then more users will notice it and ask about it.
We should be patient to see changes. When? I have no idea. These are all guesses. Until some new change is noticed, or some Avast Team member can reply with concrete info, there is no point on repeating our posts or assumptions. If they can (and if this is going to happen to "everyone"), they will improve it again.