Development is still ongoing, so most of the specs are not finalized yet. What is certain at this moment is:

CPU: NXP® i.MX 8M Quad or NXP® i.MX 8M Quad Mini
GPU: Vivante GC7000Lite
RAM: 3 GB minimum (subject to change)
Screen: 720×1440 high-DPI 5.7″ (glossy)
WLAN: Wi-Fi 802.11 a/b/g/n
Bluetooth: Yes
GPS: Yes
NFC: No (subject to change)
FM Radio: No
Card slot: microSD
Loudspeaker: Yes
3.5mm jack: Yes
SIM cards: One
Camera: Front and back
Replaceable Battery: Yes (with tools)
Smart Card Reader: Yes (OpenPGP-compatible)

Everything else is To Be Determined. This applies to: dimensions, weight, supported modem frequencies, internal storage capacity, maximum SD card capacity, camera specs, other screen specs, battery life, SAR values, etc.