It's the Japanese who will soon take the lead in diesel technology. We've already witnessed Honda's excellent new engine in the Accord and it will continue to expand throughout the European range.
Not only that, but the American market, currently dominated by petrol (I believe it's something like 98% of all passenger cars run on petrol!), will soon wake up to the performance and economy of diesels and start to shift rapidly. Petrol prices are rising at their fastest ever in the US and it'll only be a matter of time before diesel becomes appreciated like it has in Europe. Japanese makers have a very strong foothold Stateside and they'll want to get ahead of the domestic manufacturers as diesel demand grows.