I am considering using RBM33G boards as the base of a solar powered autonomous system with LTE connection. The device will have some sensors connected over UART, I2C, etc. and while it is possible to connect them using USB adapters it would be a pity to not use the available GPIOs and interfaces available on the board. There is as well an ADC and several jumpers for unknown hardware configuration options. Is there a chance the full GPIO mapping to all the headers gets released?

These are the undocumented headers and jumpers:
J4: seems to be a MDIO header, my board does not have any legends but this one in the brochure does https://i.mt.lv/cdn/product_files/M33G_190940.pdf
J600: two pins, one is GND and the other is labeled A-IN. Possibly analog in? Or a jumper.
J700: two pins, one labeled 5V0 and the other CTRL. Possibly a jumper for controlling something.
J601: Header with I2C, UART2 and UART3 and SPI, but several pins are not labeled in the board. Also, it seems that the UART2 GPIOs are shared with the various enable pins for the PCI, m.2 and USB voltage regulators, which makes use of the port impossible. SPI pins are grouped but not labeled individiually.
J23, J14, J13: Jumpers for SPI configuration, the only published documentation is the default config of jumpers for booting normally.

There seems to be a bit of related RBM33 GPIO discussion here -
viewtopic.php?f=3&t=167822&p=826607&hilit=gpio#p826607

Is there any documentation on RBM33G connectors ?

It seems that a detailed description of the RBM33G pin does not exist or is not published...

There is no response from the developers to our pleas.

In general, Mikrotik has not released OEM boards for a long time. It would be nice to release a new board with the performance of the RB5009, built-in two wifi 2.4 and 5 GHz, mini PCie for the modem and M.2 for the SSD and modem, as well as a full-fledged GPIO.