Upscale thingy is not a 540 upscaling has almost no effect. Look at upscaled DVD and Bluray but in games its even worse. The difference is so minor and the games are upscaled anyway from resolutions like 800x1440 to 1080p. Upscaling Xbox is worthless even more then an upscaling wii because the games already are upscaled to 1080p on both consoles.
A surprise could be a 360slim this could Ms bring back into the race again. But until September/oktober there is nothing which can be done a slim release would probably happen also in September/ocotber together with Natal So 1.8 Million down until September october are a real possibility. After that MS could counter again but I doubt it will be so effective that it would stop the gap closing for a long time.
Sony could also counter with a Pricecut plus Arc/ Gt5 .