Vendors would not bring out a whole new model design using brand new GPU but last year's CPU unless the new CPU was a long ways from market.  If it was only 1-2 months away even 3 you would probably take the sales hit and stick with current saving the new GPU to go with the new CPU of the same vintage.
As you said Tiger Lake H must be a long ways off.  And the even more damning evidence is that vendors with inside knowledge and even engineering samples in some cases, don't seem to think working chips are coming anytime soon.  But next gen portends a switch to pci-e 4 which impacts storage as well as GPU as well as direct to CPU TB3/4 connections (even if they are pci-e 3 based).  So the question will be for buyers, old Intel cpu+new 3xxx gpu?, Cezanne+3xxx gpu or wait.  And since Intel may not even hit their next "release" date goal as they have been failing these for years, how long will folks wait?  And will Cezanne come in enough quantities to satisfy demand?  If Cezanne comes in quantity Intel may have few people left to sell to in 6 months.  3xxx chips could also be rare too, so the picture could  be very complicated.  But certainly it appears to be a winning hand for AMD, great chip, great opportunity, no credible competition.  That at least bodes well for buyers.