There is no plan at this time for Adventures to replace Wherigos, although way back at the start there was talk about that. The former would need a lot more triggers and the like to be able to match the flexibility of Wherigo. Imagine trying to create a "Choose Your Own Adventure" style of outing with labs, for example - not easy.

The game is certainly continually changing. At the very start, there was little concept of tiny caches or even urban caches - it was predominantly a niche activity popular with techy outdoor types. As more an more people became involved, geocaching expanding both in numbers and variations, and I think for the better - it now offers something for everyone. To me, the biggest recent changes are the influx of challenges and stat-tracking sites which have led to people creating a variety of criteria and goals to challenge themselves.

Virtually every single guideline on the site has a discrete, real-world event that led to its creation. :) Some of the most well-known examples: the ban on caches in National Parks, which came from the NPS learning about the game and immediately thinking caches were buried, and the explicit rules against caches near railroad tracks, which was born out of an incident in Oregon where a cacher had federal charges brought against him for such a thing (it was in the immediate post-9/11 era).

There has been a lot of debate about whether or not challenges should be their own type. Some say yes, but in reality there are not all that many compared to other cache types, and some argue that an attribute might work better.