There was a gorgeous 108 listed here on WBF for a couple months that couldn't sell at under $11k USD. And that was before the knowledge of a Model Two. So I'd definitely agree that now isn't the time to buy a Model One. A few more should hit the used market in the fall when the Model 2 is released and prices should be even better then for anyone interested in a Model One.
It depends on the price of the upgrade, and mostly on the upgrade schedule. Unfortunately the factory seems not to be able to carry the upgrades in a reasonable time - some people gave up on DartZeel because of successive postponing of upgrades and presentation of new models. IMHO it is why the NH108 or even the NH18s are sometimes being sold at such low prices. But at current low prices, for a patient audiophile an used DartZeel is an excellent deal - and even old models sound great!
There is also a lot of misinformation going around concerning their new products and upgrade prices - in fact I have not been able to read any official statement on this subject, just rumors from users who get private news from Herve or dealers.