Boeing Marketing changed to -8, -9 etc.
However, once you really buy the
aircraft, you get your full 3 digits.
For example ANA is not operating
787-8, but 787-881. Lufthansa is not operating 747-8 but 747-830. Just the same
since 50 years, but marketing needs something new now and then to justify their
existence...
I'm not so sure about that. It's certainly true of the 747 - you will find the -830 series designation, for example, on the Type Certificate.
But for the 787, the only certificated variant (as of yesterday's update to the TC) is the -8, with no reference in the TC to individual customer numbers, which suggests that for this aircraft those are purely marketing and/or Boeing internal designations.