It looks like there's going to be another large exhibition this year at Long Marston - RAIL2015 - on 16 & 17 September.
This event isn't sponsored by Network Rail like the previous Rail Live 2014 and National Plant Exhibition 2013 events, which means there isn't likely to be as much emphasis on plant this year. Instead the focus is on innovation & ingenuity in the wider rail industry.
The exhibitor list (so far) has a few familiar names including Aquarius, Avondale, Geismar & Quattro. With two months left, I'm sure the list will grow.