The next 12 months will be some of the most important in the relatively short history of two premium Japanese brands – Lexus and Infiniti. Lexus, because it launches the new IS saloon (and coupé), while Infiniti responds with an all-new G-series.

Both compete in the most fiercel-competitive premium sector that includes BMW’s 3 Series, Mercedes-Benz’ C-Class, Audi’s A4 and Volvo’s S60. There aren’t a lot of weaknesses to exploit amongst this group, so both IS and G-series will need to come out fighting, and be able to differentiate themselves in some genuinely unique way.

For Lexus, this is the moment where the brand starts spending the goodwill banked by its 552bhp LFA. Admirers of the brand since the LFA went on sale in 2011, will now be able to buy a (relatively) affordable sports saloon featuring some of the LFA’s design cues.

Of course we’ve already seen a glimpse of the resulting end product – the stunning LF-CC Full Hybrid coupe concept, which first appeared at the 2012 Paris Motor Show, is said to have inspired the new IS, which has been completely redesigned, inside and out.

For Infiniti the stakes are even higher. With the global economic downturn putting the kybosh on its European launch plans, the new G-series represents Infiniti’s second chance to let buyers know there’s another premium Japanese brand, with great customer service and a long-list of standard features.

Infiniti are aiming for a 10% share of the global luxury car market during the next four years – which is huge, given this would be an increase from 150,000 cars in 2011 up to 500,000 cars by 2016.

Much of the responsibilty for achieving this will be down to the G-series, so this might just be the toughest battleground for the new Lexus IS as it takes market share from the Germans while protecting its back from its Infiniti rival.

The new IS will be revealed on Tuesday, January 15th, 2013 at the North American International Auto Show in Detroit.