Let's not over-estimate this. The price is so low [0.165 billion US$] because Toshiba has a very small share of the total sensor market (I have see 2%) and I believe it has been losing money (the sale comes with Sony assuming debt too). So it is not increasing Sony's market share by much (maybe from 40% to 42%). Also, I understand that this is mostly an acquisition of fabrication capability, and there are plenty of third-party fabs out there, particularly for the larger sensors like 1" and up, whose relatively large photo-sites (compared to camera phone sensors) do not need anything close to the state-of-the-art small feature size fabs. In fact, I have read that SLR sensors are often made on older equipment, whose minimum feature size is too large for making the newer generation of ever more packed camera-phone sensors, CPUs and memory chips. For example, the Aptina-designed sensors in some Nikon One cameras are outsourced; nether Nikon nor Aptina has fabs for this.
So I do not see much reduction in competition. We photographers tend to focus on our main interests, and so look at the bigger sensors (say 1" and up) that are a small fraction of the total sensor market, which is in turn only a part of a far larger CMOS device market. Competition for Sony Semiconductor Solutions in the market for "sensors bigger than the ones in phones" will continue to come mostly from Canon, Samsung, Panasonic, Aptina/ON Semiconductor, CMOSIS, and so on. (And if Canon needs to in order to maintain its lead in the ILC market, it could concentrate more on sensor design while outsource more if its fabrication.)
P. S. to put the $165 million dollar sale in perspective, Nikon's other sensor supplier Aptina was acquired last year by ON Semiconductor for a substantially higher price: $400 million. By the way, ON also owns what used to be Kodak's sensor division (now called TrueSense).
