12-60mm f/4.0-5.6 would be ideal for M4/3

A 12-60mm f/4-5.6 when the 12-50 is already available would be a waste of time and resources.

Make the 12-60 an f/2.8 and make it focus as quick as the 12-50 and I'll buy one. But the last thing we need is another slow zoom that nearly duplicates an existing lens's focal length.
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Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life.