The big news in the processor world in 2015 was the Qualcomm Snapdragon 810 and its heat problems. Samsung actually opted to use their own in-house Exynos 7420 in the Galaxy S6, Galaxy S6 Edge, Galaxy Note 5 and Galaxy S6 Edge+ this year, instead of the Qualcomm Snapdragon 810. While Samsung didn't give an official answer as to why, many analysts believe it's due to the heat issues. Additionally, many other smartphone makers skipped the Snapdragon 810 and used the slower Snapdragon 808 in their devices. Qualcomm officially announced the Snapdragon 820 last month in New York, which is now a quad-core chipset instead of an octa-core like the Snapdragon 810. While Qualcomm says that it doesn't overheat or get much more warmer than normal, it appears that it might still get a bit hot.
There are various rumors and reports going around that Samsung is going to use the Snapdragon 820 in their Galaxy S7 that's due out in early 2016. As well as using an Exynos chip for other markets (typically Exynos is for 3G and emerging markets and Qualcomm for LTE markets like the US and Canada). Which is something they've done in previous generations of their flagship devices. Now there is a rumor coming out that Samsung is actively looking for a supplier for heat pipes for their new flagship, the Galaxy S7. To many this might mean that the Snapdragon 820 does still get hot.
However, sources are also stating that Samsung has not made the final decision whether a heat pipe is necessary or not. Which should tell us that the Snapdragon 820 doesn't overheat as much as the Snapdragon 810 did, but that Samsung might still be a bit worried about the temperature inside depending on what the user is doing with the device. Samsung is said to make their final decision before the end of 2015, which is less than 30 days away.
Rumors have pointed at Samsung announcing the Galaxy S7 as early as January. This is due to the sales for the Galaxy S6 this year, which weren't as good as the company had hoped for. Typically, Samsung announces the Galaxy S at Mobile World Congress. Which is February 22-25th, 2016. So that would be quite a bit earlier than normal.