DCS is not dead, but being re-invented. But there are several problems that are rooted in software design (not hardware).
I can find you 100 well designed hardware gadgets for every good piece of software that is out there. And the fact that industry has had the MSFT blinkers on has made life rough if you are into new possibilties. Most vendors in North America have not even considered non-Microsoft-based solutions. The result: mediocre performance when compared to real traditional DCS. Even when MSFT is used in DCS the conveniences are there, the system design and performance isn't.
There is good news. You take a world-class operating system like Linux, with object based software (IEC-1131 compliant), and a well thought system design voila!
One "Dell" Server can equal (=) what (in Honeywell speak) 6 HPM's, 6 GUS, 2 HM's and 2 AM's do, or replace 12 MFC's, and 6 PCV's (Bailey), etc.
By reduction in hardware, increased software power the cost plummets - by 2/3rd's and the time to project completion can be reduced by up to 80%.
The future is sofware based systems, with thin clients, net based clients, using Linux or Posix compliant OS.