I have heard of this in a number of cameras, not all Sony's. If it is, as you say a micro-wiggle then I think it is probably just the built in manufacturing tolerance and is considered normal by Sony. If it occurs with one lens only then it may be wear in the lens, or possibly due to the lens being at one end of the tolerance scale and the camera mount at the other. In any case I don't think micro wiggle is anything to worry about, but that is your call.
Take it to your retailer and have them look at it and your lenses and give their opinion.
Sony A7, A850, A77, A700 || Sony>> 70-300G, 28-75 f2.8 SAM, 16-80CZ, 50 f1.4, FE 28-70 OSS, FE 24-70CZ f4 OSS, LA-EA4 || Minolta>> 300 f4 G HS, 200 f2.8 G HS, 100 f2.8 (D) Macro, 50 f1.7, 28 f2.8, 28-135 f4-4.5, 70-210 f4, 500 f8 Reflex, TC x 1.4 HS, TC x 2 HS. || Sigma 21-35 f3.5-4.2. || Tamron SP 24-135.