I am now the proud owner of a single Raspberry Pi 4, with another 3 on the way. Obtained from ThePiHut. From initial viewing it is a fabtastic piece of kit, sporting the following specifications:

Key features include:

• Quad core CPU @ 1.5GHz
• Dual display supporting up to 4K resolution
• WiFi
• USB 3.0
• Bluetooth 5.0
• Available in three RAM sizes; 1GB, 2GB or 4GB!

Specifications

• Broadcom BCM2711, Quad core Cortex-A72 (ARM v8) 64-bit SoC @ 1.5GHz
• 1GB, 2GB or 4GB LPDDR4-2400 SDRAM (depending on model)
• 2.4 GHz and 5.0 GHz IEEE 802.11ac wireless, Bluetooth 5.0, BLE
• Gigabit Ethernet
• 2 USB 3.0 ports; 2 USB 2.0 ports.
• Raspberry Pi standard 40 pin GPIO header (fully backwards compatible with previous boards)
• 2 × micro-HDMI ports (up to 4kp60 supported)
• 2-lane MIPI DSI display port
• 2-lane MIPI CSI camera port
• 4-pole stereo audio and composite video port
• H.265 (4kp60 decode), H264 (1080p60 decode, 1080p30 encode)
• OpenGL ES 3.0 graphics
• Micro-SD card slot for loading operating system and data storage
• 5V DC via USB-C connector (minimum 3A*)
• 5V DC via GPIO header (minimum 3A*)
• Power over Ethernet (PoE) enabled (requires separate PoE HAT)
• Operating temperature: 0 – 50 degrees C ambient

* A good quality 2.5A power supply can be used if downstream USB peripherals consume less than 500mA in total.

My plan is to build a 4 Node Docker Cluster.