I'd say a lot of the 'old hands' have quit, or are not playing much at all while waiting for AH2. While numbers aren't decreasing, the overall "quality" of the experience definately is. At least in my opinion, the focus of the game has shifted from air combat to "building battling" as Lazs would put it. The game has never been very 'diverse' as far as what planes you see, but constantly seeing the same 4 planes over and over and over and over and over and over and over ad nauseum burns people out a bit quicker than I'd say is 'normal'. Personally I've been in a constant state of burnout for about a year now, occasionally I'll fly a lot when I "re-discover" how enjoyable some planes can be to fly (the 109G-6 was my last one) only to get run down by la7s and chewed to bits by 5-20 people (depending on how large their pack is at the time) several times in a row reminds me of why it is pretty much a waste of time to fly anything other than the la7, spit, n1k (those 2 in packs), or P51 in the MA (or the 109G10 if you are feeling brave and lucky, and are a great shot).
Pretty much a 'fight' in the MA terms starts when the Tiffies come in to pork the fuel at the field, and ends when one side gets more la7s, spits, n1ks, and P51s than the other side. It is extraordinarily rare for a fight to just 'develop' between two fields, people are to afraid to go towards an enemy base unless they have 25 other people with them, which pretty much ends any chance for a fight as soon as all the dots start popping up on radar. Yes, occasionally you will get some idiot that enjoys being vulched 4,000 times (which is why I think the vast majority of the 'mishuns' can maintain cohesion while they take field after field), but usually its just pork the fuel, kill the ack (and yes... in that order, nowadays), kill the town, take the field, repeat.
Just 'patrolling' an area used to be a good way to get 5-6 kills a sortie, you could find other people doing the same thing and get in multiple 1v1 fights. That doesn't happen anymore.