It is worth bearing in mind that a majority of GA training organisations seem to be losing sight hat it is less about the number of seats in the aircraft that matters, and more about the service provided. I believe that how a service provider makes a customer feel will be remembered long after the cost of the service is forgotten...
Let's see - a mix of two and four seat aircraft is good, as it provides options for customers. Two seat aircraft are likely to appeal to the price sensitive client - even thought the actual cost comparison between them and a four seater may not be massive, the perception that a four seater is more expensive is relevant to the relatively uninitiated buyer of the product. I would rather fly a clean, well presented two seater in good repair (ie everything on board works, including the clock, and no grotty and broken plastic trims...) than a weather-beaten daggy larger machine. Further, the staff need to actually genuinely care for their company and product, not just see the customer and the organisation as a revenue generator or vehicle to knock up some hours before disappearing to fly charters. These points seem like no-brainers, so why is it that so many operators fall into these traps?
I think that the path to success for GA training providers can still be followed / achieved and be (almost) like the "good old days", but it will involve careful consideration of many aspects and the appropriate mix of all these elements, with undoubtedly a dash of luck and disciplined business acumen.
Back to topic, I think the value of two seat GA aircraft has been forgotten of late and I imagine that there will be some level of resurgence for them, especially for those keen enough to manage the continuing airworthiness of the tried and true types like the 152.
BTW, the 162 is a crock and surely could not be considered representative of what a good two seat trainer should be!!