To be honest, the move is probably towards km simply because today's children and young adults were brought up on metres/kilometres/grams/kilograms/Celsius at school. Sure they were told about miles/pounds/Fahrenheit but I'm sure that they think in metric. I can estimate in both metric and Imperial, but I think in Imperial (more of this in a mo).
Likewise, some of us can use both. I'm happy to say that light travels at 186,282 miles per second or 300,000,000 metres per second, that the Sun is 93,000,000 miles away from the Earth or 150,000,000 kilometres. I'm not bothered, I can use both. Mars is 142.5 million miles or 228 million km from the Sun on average. I don't mind using miles or km (although I have been teaching science long enough to have the km distances engraved in my brain!)
I'm also sure that programme makers have to cater for a wide audience - those that use/think in Imperial measure and those that use/think in metric - and use both sets. This is also true of the weather forecasts where both Fahrenheit and Celsius temperatures are quoted. Bizarrely, I think that zero Celsius means that it is going to be chilly today but in summer I know that it will be uncomfy when it gets to the high 70's / low 80's (Fahrenheit of course).
In typical fashion, the UK fumbled the issue in the 70's and early 80's when we were going metric but did so half-heartedly - which is why we have such a mess as far as our units go, an example being that we talk of petrol consumption in miles per gallon (mpg) but have petrol priced in litres (and although on the car forecourt/brochure or website the fuel consumption may be quoted in litres per 100km, how many folks honestly can say that their car averages 8 litres per 100km instead of 35mpg. Not many I'll bet!)
If you want a further example - try buying timber - you can get 1.8m, 2.1m, 2.4m and 3m lengths of timber at Wickes and B&Q - why? Well these are multiples of 30cm (= 1 'metric foot') so 1.8m is a 6-foot length, 2.1m = 7-foot, etc, etc). Or go and buy some cloth off a roll at a department store or habidashers. The cloth comes in 36-inch or 48-inch widths but you buy it priced 'per metre length' - aaaarrrrggghhh!
Personally (although it seems to be capitulating to Europe & Napoleon here) the metric system is much more self-consistent and logical. Who in their right mind (whatever the historical reasons my be) would come up with a system where we have 12 inches to the foot, 3 feet to the yard, 1,760 yards to the mile (or if you prefer 63,360 inches to the mile) - what a crazy system - or 16 ounces in a pound, 14 pounds in a stone and 160 stones in a ton (or 2,240 pounds) Whereas 10mm to the cm, 100cm to the m, 1000m to the km makes much more sense (all based on powers of 10), as does 1000g to a kilogram and 1000kg to a tonne.
The only beef that I have with the metric system is in the units. Capitals signify larger multiples (eg M = mega = million, G = giga = billion, T = tera = trillion) and lower case signify smaller multipliers (eg m = milli = thousandth, c = centi = hundredth), but the multiplier k = kilo means thousand (!) - again, aaaarrrrggghhh!
Anyhoo, rant over
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