I think it means that their testing has determined that releasing both Navcore 8 and map version 8 for x20 devices is not compatible with their marketing plan, and that version 8 maps won't be released until there are very few (if any) x20 models remaining for sale to end users.
Releasing version 8 maps for x20 devices would mean that anyone who purchased an x20 device in the past 30 days would get the functionality of an x30 device for free, and would temporarily boost sales of the remaining x20 devices while at the same time cutting into sales of x30 devices.
Basically they want the timing of the release to enable few (if any) x20 owners to get a free update to x30 functionality. Barring the current fire sale on maps, version 8 maps are selling for around $130US. If they can delay the release and eventually get people to buy these instead of giving it away...
I agree with this. TT needs to raise their profits. Particularly so since their profitability dipped in their latest yearly financial report and their need to raise cash for the Tele Atlas costly purchase. The x20 stock needs to be liquidated first, then those buyers will need to purchase v8 maps is the scenario I envision the most likely to occur. Don't expect giveaways from a company that strongly needs to substantially raise its profits! I would not be surprised to see v7 maps for the 7xx and 9xx models to be discontinued to force v8 map purchases...