In the past, Quad-Core processors used to feature in the most popular Systems-on-Chip (SoC), but later Octa-Core processors nabbed the 'highest speed' tag from them.
At present, all the SoC manufacturers including Samsung, Qualcomm, NVIDIA, Intel and MediaTek are busy making budget 64-bit Octa-Core processors. Going a step ahead, MediaTek is reportedly working on multiple chipsets which might feature 10 and 12 core processors inside.
Currently, there are several budget smartphones available in the market which feature Octa-Core processors; Yu Yureka and Wickedleak Wammy One are among them.
According to a GizChina report, MediaTek has already started working on the chipset. Codenamed as "Bomb", the chipset might feature either 10 (Deca-Core) or 12 (DoDeca-Core) processor inside. The new "Bomb" chipset will be based on ARM architecture and will help MediaTek to replace the current leader in mobile chipset manufacturing - Qualcomm.
If you notice, most of the time our smartphones are not able to utilize all the cores featured in them. More cores also mean more battery/power is being consumed; however, they qualify the marketing gimmick - more is always better. And, probably that is the reason behind manufacturers being keen on featuring more powerful configuration on their smartphones.
Meanwhile, NVIDIA has also released their new Kepler-based chipset - "Tegra X1" - which retains the same Octa-Core processor inside, but features a 256-core Maxwell GPU. The Maxwell GPU architecture gets used in NVIDIA's most successful GPU's including GeForce GTX 980.