Apart from the quote provided by Canon Rumours Guy, a few others leapt out at me:
"If we were to consider producing digital camera bodies only, it could be easily moved outside Japan. Production and assembly of digital cameras are not – in spite of appearances – that complicated. Manufacturing of high quality lenses, on the other hand, is an incredibly ambitious challenge, which requires the best technologies – and the best people."
"As regards the use of electronics, SIGMA is not a traditional company, but rather a very modern one – modern lenses more and more often resemble computers, equipped with processors, memory or internal software." ... "Development of such software requires team effort from many people, while a modern, high‑quality optical system can be designed by one experienced engineer."
"Photography market is indeed getting smaller – but it won’t be getting smaller infinitely. According to our estimations, it will reach its minimal size next year, in 2021 – and since then it will stay pretty stable. I would compare the ultimate size of this market to the level of camera sales in times of traditional photography, before the great digital revolution. The true number of passionate people, who want to make photos with high‑quality cameras and lenses is now – and was then – probably very similar."
"We still intend to produce digital cameras, while not necessarily these have to be models with Foveon sensors (although we are still developing this technology). We will be producing them for two reasons: to honor the memory of my father (who always wanted SIGMA to also be a camera manufacturer, not just a lens maker), but first of all for much more practical reasons. Designing and producing cameras makes it incredibly easier to design lenses as perfectly as possible, as it’s only the combination of camera and a lens that allows us to register an image. Modern camera bodies are as crammed with electronics as lenses, which is why the final quality of an image largely depends on how this electronics communicates and cooperates. Not only equipment, but also software is of utmost importance – nowadays it’s the software that has a decisive impact on the final quality. This is why the experience we gain designing and selling cameras is invaluable for us, though – frankly speaking – we still lose considerable amounts of money in this area. However, until I see even the smallest chance for us to start making money also by selling cameras, we will go on developing them. And so far I believe such a chance exists."