Last times there were sounds of Digic 5 was 7D then 1D4. Canon is getting a lot of mileage out of 4; it must have been quite a solid design.
I'm thinking 60D is more 4; I don't expect the camera to do anything beyond what Canon has already released. 1Ds4 as the first 5 is my guess--a new processor to match a new cutting-edge sensor. Perhaps updated to be programmable even?
Maybe you're right. Now that I consider 50D, which is 15MP at 6.3fps, so Digic 4 can do at least 18MP at 5.3fps for 60D. Not great, but enough for me.
Another version is also possible. Most often camera companies introduce interesting new features/processors first on lower level DSLRs, even on compacts ad only then after "real-time" testing they bring these features onto higher grade bodies. My point is that most probably 60D has several features which are same or even better than 7D (say 19 AF points - same, Digic 5 - better), therefore they deliberately make 60D feel amateurish in other aspects - for example plastic body and swivel screen. By doing this they won't hurt 7D sales much, until 8D comes with features same and better than 60D. Actually that's one of the reasons that body release cycles are shifted so that the neighbour bodies are introduced about 6 moths after each other (like T1i, 7D, T2i, 60D then T3i, 8D, T4i, 70D etc).
I would really hope that Canon splits XXD series into two: XXDv - video oriented (hope it's 60Dv which comes 26th August) and XXDs - stills oriented (60Ds, no swivel, high ISO, better sensor etc, say to be announced in fall). But the chances of this are zero, because Canon would have to put too much effort for such artificial subdivision and the benefits of this in terms of sales are really questionable. So if my hopes won't come true, then it means that at least in semi-pro and lower grade bodies Canon, in contrast to Nikon, does not put much efforts to make these PHOTOGRAPHICALLY better. Pity.