Going back a few posts, I think the issue of backwards compatibility is an interesting one. As I've mentioned before, I've been a Cubase user since almost the very beginning (version 2 or so on the Atari). Then it transitioned to Cubase VST, then SX, and now just Cubase. At each of those points compatibility was somewhat broken - I mean I'm fairly certain it's hard, if not impossible, to load a Cubase VST project into Cubase Pro 10. At least not without some major headaches.
So the fact that Reason 10.4 will open Reason 1 projects like it's no big thing *is* kind of amazing. But if, hypothetically, Reason 11 or 12 was a HUGE paradigm shift that required me to keep 10 installed in order to load my projects and prepare them for transfer to a new version...I think I'd be okay with it. I'm not necessarily saying it *needs* to happen. I mean I'm struggling to think how different things could really be. The only thing I can imagine changing significantly is the sequencer. That's where most of my wants/needs are. The rack is the rack and I'm pretty happy with how that works. The mixer could probably do with some love as well (themes, channel presets, etc.). But yeah, sequencer is where it's at for me.
Folders
Crossfades
Automation curve handles
MIDI note chase
MIDI note preview on arrow nudging/selecting
Expanded toolset (parabolic and LFO style line drawing in velocity lane, "tilt" handles for selected velocities)
More/custom colours
Option to snap recorded events to current grid resolution rather than keeping relative offset (even though it is useful at times)
Adding all F8 functions to menu items
Beyond that, a new browser is a must. Quicker, indexed searching. Racks tagged and filterable by category and type; not just developer. I also think a great idea would be to make the left pane multi-function. So the browser and file system could be in one tab. Track controls in another. This could incorporate ReGroove like functions and realtime MIDI transformation such as transposition.
And...custom keyboard shortcuts!
Oh and right click a samples -> send to NN/Grain/any device with sample loading
The wishlist grows every day haha. But I'd settle for the first 5 or 6