Instead of the GIMP limping along behind PhotoShop, both dragging their decades-old legacy baggage, monolithic architectures, 1990s pricing models, etc., into the foreseeable future, I wish we had something more like Octave, SQLite, or Python: a powerful, faceless dev platform on which to build graphics-processing apps.
Basically, a runtime that holds a GPU-optimal image model (raster layers, vector layers, non-destructive edit management, multi-session undo, etc.), a set of APIs for sending memory-protected commands to the model, and a growing standard library of routines that have proven useful (network comms for offloading some processes or results to "the cloud", input/output codecs, CSS3, whatever). It would have a relatively easy to use scripting language with some built-in data types such as layer, region, vectorPolygon, gradient, font, etc., plus the usual lists, dicts, first-class functions, etc. Scripts that get a lot of use could be reimplemented in C, etc.
Developers could wrap whatever GUIs they wanted around this engine, creating easy consumer apps such as a slideshow or a camera-to-computer file importer with a magnifying glass and a keep/delete shortcut, all the way up to building clones of PhotoShop, Illustrator, resurrecting Fireworks, and so on.
Maybe someone would build a GUI builder for it that let you drag image rectangles and buttons into a window and script the whole thing, so non-programmers could create lens comparison apps, blink comparators for comet hunting....
I'd so much rather have a platform like this, where the hardest part--the image engine--would be done by experts, and the apps themselves, the feature sets, the UIs, could then be built by hordes of amateurs.