Well the obvious for both capacity and performance.
I'm assuming the 2BOX architecture is similar to a PC so some of this might be hit or miss. So just use them as guidelines and substitute them for what actually matches the module.
A faster processor.
More RAM
SSD drive.
Ever opened the 2Box? We did for the MOD and it is more complex than you expect. PCB is nicely designed but there is not much on there to change or upgrade. BTW, performance is top notch and the only outdated component is the USB 1.1. The module has been developed in 2007-2008 and still ahead of the competitors.
i think it is very likely that the next version of the 2 Box module will have a faster processor, more RAM on board, a faster storage system, and of course a faster USB system.
i'm sure that 2Box have already hit the limits of the amount and quality of realtime processing that can be done on the sounds. the module will need more RAM and processing power to support, for example, better delays and reverbs...