Like you I'll put incredulity aside for a moment...
I certainly agree that the 70-300 should be an early introduction but I'd guess that one of the pancakes, probably the 14mm, should come before it simply for the marketing guys to be able to claim bragging rights on size, or lack of it.
The pixel density might be a concern but that 3x3 pixel binning for 1920x1080 video could
explain the choice. That would require 5760 pixels horizontally and, for square pixels on a 3:2 stills format, one then needs 3840 pixels vertically giving a grand total of 22,118,400 pixels. Each pixel would be about 9.7 µm2 in area. If I've got my sums right that's about half the area of the pixels on the 7D. The 7D is rated from ISO 100 to 6400 with expansion to 12800 so the putative EIS 60 spec, at full resolution, of ISO 100-6400 might be a little optimistic but not madly so.
I reckon that either the creator of the rumour has done his or her homework or the leak is genuine. Probably the former, though I hope not, but if Canon hasn't actually got an EIS 60 on the drawing board they darned well ought to. So long as the quality of construction and ergonomics impress I can see a lot of Canon owners being tempted even if the price is quite high. I'd love the opportunity to have a largish sensor in a small body which also provided me with full AF compatibility with my current lenses. My 70-200mm would effectively double in focal length to a 140-400mm f/4 from what it can do on my 5D2. Given that the current EF 100-400mm f/4.5-5.6L IS USM is priced well north of £1,000 the EIS 60 might be quite a bargain even if the high ISO noise tests show a realistic limit of 1600.