I would like to see the carry-on to go away. I understand the consequences would be quite harsh at first, but I do believe the airports and airlines would eventually figure out better ways to handle luggage and we would all be better for it.
I can't find a lot of information online, but I remember an airline employee telling me that the "P90 SLA" for handling baggage at big European airports is 20 minutes.
I don't think there's a lot of room for improvement, let alone a dramatic increase of the volume of checked baggage.
The improvement doesn't need to come only just in form of time to luggage but also in the experience for offloading and pickup it up. Also reliability is quite an issue (if you ever flew through CDG you know what I'm talking about).
I would like to see some more innovation around luggage handling.
