Not all software evolves that quickly which means the processing needs also do not jump. Today we are running 8 year old Panasonic Toughbooks and would not be thinking about replacing them if the hardware was not worn out. It's not a matter of needing more horsepower, it's a matter of needing durable hardware. It's important to match the machine with the need and the need does not call for disposable hardware. Besides, when it is time to replace the Data 911's, all that needs to be replaced is the PC unit for under $2k. That is exactly what the site we visited yesterday was doing and according to them, that alone saved them six digits on their replacement costs compared to a Toughbook.
Personally, I don't think the link you provided will fit the bill. There's not a lot of detail on the hardware used, but I can tell you right now that a 7" display would be all but useless for us.