Tomtom has a history of rolling out its latest software to models sold about 2 years back, eventually.
They usually wait 3-6 months from the initial release. I don't know if it's a marketing strategy, or if it takes their developers that long to roll out the whole product line.
For example, navcore 7 rolled out to all models except the x00 line, navcore8 rolled out (in some form) to all models except the x10 and some ONEs.
Our currentworld of multiple model-specific versions of navcore reminds me of a few years back when tomtom was in the middle of the navcore 7 rollout. Back then the different navcores seemed to come out every few weeks fixing bugs. Eventually, all products were updated to a single Navcore.
My guess is that the same thing will happen with navcore 8, probably by end of spring. However, I assume any devices that were offered navcore 7.9 are at a development dead-end.