Does anyone know if it looks likely that more buffer memory is going to be leveraged in the future? Every bit is precious in this case 
I've heard nothing, but when looking at the screen when recording i do often see unused mb/s & empty buffer blocks that, in theory, could be used but the recording stops.
The problem is really about the development of the 5D3 over every other model (which is understandable) & i don't think the developers actually have a 60D. It would be v.welcome to squeeze out more, but if you look at the other models in our category (minus the 50D), then we really are getting great results.
As far as quality is concerned, i have found that 1280x... is absolutely fine for upscaling, but you need to manually follow the ETTR rule (not the module for photos) in order to reduce sensor noise. And you've got to remember that the old H264 was absolutely shit compared to most RAW resolutions upscaled. Further to this, RAW is only going to be useful for fictional story telling & not Doc style run'n'gun.
I've just shot a music video [experiment] for a friend using 13sec bursts & that was just about long enough. However, you still have to factor in Moire/Aliasing, as its still there in abundance & i think it shows up more than it did with the H264!