It's hard to imagine how else a reverberation, added after the fact, would work in any other way than a dry-wet scenario. That's simply what you're doing... adding reverberation (wet sound) to a, preferably, un-reverberated source (dry sound).
What's being controlled in that case are the cues for the balance between the direct sound that reaches the listener's ears first (aka the dry sound) and the the early reflections+reverberation (aka the wet sound) that the resonant characteristics of the space the sound appears in provide. Having control over that dry-wet balance allows the sound designer to vary the distance the virtual instrument appears to be from the listener.
Of course, having control over that balance means that one can easily create unbalanced, unrealistic mixes. That's where MIRx and Natural Volume are useful in that, together, they provide an optimal relationship between multiple sound sources and reverberation of the modeled space. There's still dry/wet balance to control the cues the ear uses to detect the distance from the listener to the orchestra.
But, at the end of the day, it's still a simplified model of richness and complexity of what goes on in a real-world situation of sound events occuring in real space. There's an infinite number of unique positions for sound event and listener. Acoustic and psychoacoustic research works with the notion of a "just noticable difference" (JND). There are differences that are so small that we can't perceive them. This suggests that we don't actually need the infinite set of impulse responses to work with, but that there will be some large set of impulse responses that exceeds the JNDs for any given space. Like sampling rates that only need to reach a certain rate before we can't hear any difference any more this suggests that we'll get to a point where, using the convolution technique, it will be as good as it can get.
I've poked around on the net and can't find any current research that goes beyond the multi-impulse convolution model. I'll bet quantum computers, when they're finally up and running at full bore, will provide a breakthrough though.
