MediaTek Helio X20 is the company's first chipset with a tri-cluster deca-core processor (2x Cortex-A72 @ 2.5GHz, 4x Cortex-A53 @ 2.0GHz, 4x Cortex-A53 @ 1.4GHz). The X20 is ready for mass production, and some reports suggest the Meizu MX6 will be the first smartphone to utilize it.
The Helio X25 is also in the pipeline, and we'll be seeing it on an upcoming LeTV Le2.
It seems MediaTek has already begun to work on the Helio X30 successor even before we see the X20 and X2 in action. The latest reports suggest we'll be seeing the first X30 smartphones in early 2017.
The Helio X30 is also rumored to bet on the tri-cluster CPU design, with 2x Artemis cores at 2.8GHz, 4x Cortex-A53 at 2.2GHz, and 4x Cortex-A35 at 2GHz. The Artemis core by ARM design is the successor of the Cortex-A72 and should battle with Qualcomm's Kryo solution. The A35 are extremely power efficient and offer up to 40% faster performance than their Cortex-A7 predecessor.
The Helio X30 should bring a powerful 4-core PowerVR 7XT GPU and support 26MP snappers, dual camera setups, VR connections, and LTE Cat.13.
MediaTek is rumored to manufacture the Helio X30 by TSMC's 10nm FinFET process, which means up to 100% better power efficiency than its Helio X20 preceeding generation.
All of these are just rumors, so you should take them with a healthy pinch of salt.
