I'd suggest that you're currently seeing it happen with the development of the Daystate electronic trigger/air metering. Consistency leads to accuracy, so properly controlling the delivery of air behind the pellet has got to be the way forward.
Personally I feel that there ought to be something better in the way of pellet design, but what has already been achieved with the diabolo shape is quite impressive.
Increasing the air reservoir pressure, IMHO, is a dead end - compressing air to much over 300 bar is an increasingly inefficient process. I believe that 400 bar diving cylinders were tried out years ago, but there were problems due to the heavy cylinders and the requirement to use a three stage (rather than the current standard two stage) regulator to step the pressure down. Expanding air from such a high pressure generates some serious cold!
Semi-auto PCPs would be popular, I'm sure, but IIRC there is some bizarre agreement between the UK gun trade and the government not to create them, as they'd just end up being banned. Correct me on this if I'm wrong!
Probably the best way to look into the crystal ball is to step back and think about what's "wrong" with current airguns and if there's any possible way of correcting the "fault".
When I used to hunt, the thing I wanted most on my HW35 was a rapid, low movement reload, for those times when not all the rabbits disappeared after the first had been shot - this has certainly been addressed by the multishot PCP. Apart from that, it'd probably have been more than 12ft lbs power, but that's not a technical limitation - just a legal one!
I'm sure there will be all sorts of interesting and clever developments, some rubbish, others brilliant, but we'll just have to wait and see!
Ben