The 4/3 format is roughly half 35mm size. However, half-frame cameras such as the Olympus Pen series were only about 2/3 the size of full frame 35 mm cameras - excepting of course the Olympus XA series and the Minox 35mm series. This new 4/3 micro seems to lend itself to rangefinder or direct vision cameras with interchangable lenses, yet I don't think that they will be half the size of present DSLRS or even half the size of a Leica M8.
The telecentric lens design is predicated by the general design of sensors, though clever arrangement of micro lenses can negate this to some extent - makers such as Nikon have stuck with a throat opening designed in the 1950s, when the problems with non-parallel lens design and ultra-wide angles where unthought of, and so need to look for an alternative if they are to keep compatability with older cameras and lenses - telecentric lenses need a fairly large lens throat - so Nikon are to some extent prisoners of their own unwillingness to change - and you might say that their lenses etc are triumphs of design over common sense. I'm not an Olympus owner, but I appreciate the concept behind starting from a blank sheet of paper when it comes to integrating lens and sensor design - no other DSLR maker has done this, and it is arguable that they are in part lumbered with yesterdays technology.
Olympus seem nowadays to have largely overcome the noise problem associated with their relatively small sensors - and lenses for this new design ought to be considerably smaller than the retrofoucs designs for DSLRs - just compare the enormous sizes of lenses for the average DSLR to those of comparable focal length for a rangefinder - I don't see any advantage in largeness in lenses just for its own sake [unless you want to make a priapatic statement
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However, the viewfinder for any presumptive rangefinder camera looks like being a weak area at present; electronic viewfinders have a rather coarse pattern, and 'chimping' has its own disadvantages. Any optical viewfinder must allow for variable focal lengths, and yet be big enough to satisy today's users - the mini viewfinders of the Olympus XA or Minox 35mm are no longer acceptable.