I can't really predict when I will find time to implement this, it is a substantial effort, and not an advertised feature.
Some more techy details:
The processor on the Axoloti Core allows up to 22.5 Mbit/s both sending and receiving. A single digital audio channel at 48kHz/32bit takes 1.536 kbit/s, so that 'd allow 8 channels of digital audio in both directions plus more control rate channels. If there is a less speedy processor connected (Axoloti Control - in development), that 'd be max 16 Mbit/s (STM32L0).
This connector carries SPI and single-wire UART, the idea is that the UART connects all nodes in parallel for bookkeeping, and the SPI could connect in a ring network topology - every node sending to the next one, receiving from the previous.
Automatically partitioning a single generic patch over multiple nodes is a hard problem, so even when multiprocessor streaming is implemented it wont automatically spread synth voices over multiple nodes, each processor will run its own patch, where there would be an object to send/receive digital audio from the multiprocessor link.