BMW has had to make some big decisions regarding their volume seller of late. The BMW 3 Series is arguably the most successful selling luxury car of all time, so when the company decided to discontinue the 3 Series Coupe model line and create the 4 Series, you just know there were some sleepless nights in Bavaria.

Of course, in the grand scheme of things, this is no big deal. It’s not like the BMW 4 Series is going to be rubbish. But enthusiasts and petrol heads around the globe quickly realised that this may spell the end of an era for the iconic BMW M3.

BMW M4 to break the mold

We’re going to have to get used to the idea of an M4, and while we now know almost exactly what it will look like (see: BMW M4 concept gallery), speculation is rife concerning its engine configuration. BMW have confirmed some details of the upcoming M4 to UK’s Top Gear magazine.

The car will not be naturally aspirated – the first time an M3 will be turbocharged. But it isn’t the M3 remember, so its legacy remains intact. Questions still remain around the actual number of cylinders we can expect. Will it be an inline-6 or V8?

However, there are some clues. BMW say they are pursuing an “add-lightness” approach, using advanced materials and production processes developed for cars for the forthcoming BMWi3 and i8 hybrid models. That implies carbon-fibre and reinforced plastics.

With that in mind, I think we can safely bet on an inline-6 with a single turbocharger, as is the latest configuration of cars like the M135i, which I’ve driven and which is just superb and quite unsettlingly fast.

However, with both the M5 and M6 running twin-charged V8s, there is still that option on the table, although my money is on a lighter set-up with less weight over the nose.

BMW has said they are in no rush to get the M4 to market, and while they have been keeping their eyes on the competition, in the form of the Mercedes-Benz C63 AMG and the Audi RS4, they are not “targeting” their rivals, they insist they are just trying to build the best car they can, and it may take a little while longer.

But with some near-production units spied running around Germany recently, I would say we can expect the new BMW M4 in South Africa by the time 2015 rolls around.