Yes it's true that currently it would take way too long to render anything larger than regular desktop resolution size images. But given that there's still potential in optimizing the renderer for speed, plus multi-threading, plus availability of quad-core processors probably this year, we might have good reason for hope that the render times with larger images become more accessible to us.
On the other hand side, I have a TG0.9 render on 30" x 20" in my room. The source image was rendered with 4000x2600 pixels, and upscaled to match the 30" x 20" at 300 dpi. Together with its passepartout and frame, the whole image takes quite some space on the wall. However, you actually NEVER get so close to image that pixels become apparent - the picture is just too large to view it closer than 1 meter away from it.
Now, my point is, that TG0.9 full quality renders are comparable to a TG2 render at 0.5 quality, or less. With TG2 it's perfectly acceptable for most scenes to render at 0.5 quality, maybe up to 0.7 if you're ambitious. For carefully upscaled prints, that should do.
All the above - of course - pending that renderer speed optimizations really will happen. And I'm sure they will.
Best regards,
Frank