My two cents...all the Arturia synths are great-sounding plugins but only the new synths introduced from VC6 onwards actually behave and sound like their namesakes.
I'm pretty certain deep down Arturia know that their 'legacy' VSTs like the the Prophet, CS80, ARP, Moog, all need a re-write to make them sound more like their namesakes, because their recent emulations such as the DX7V are in a different league in terms of authenticity. But there is firstly the cost of resources needed to make a full re-write happen, secondly Arturia would then have a rack of new virtual instruments which are incompatible with everyone's existing presets because they don't sound the same.
It's a tough decision.