Standard communication protocols like the OPC Foundation's Unified Architecture (OPC UA) give compatible devices function blocks that are able to communicate over industry standard Ethernet using common data models.
Using proprietary protocols to access a range of machines is no longer necessary because of the widespread application of international standards based on OPC UA, PLCopen, and industry standard web services.
Furthermore, communication isn't limited to the factory floor. These standards transcend the automation pyramid and allow PCs on the enterprise level to transfer information with sensor level devices.
The IoT looks like it will continue its merciless path to connect more and more machines, as well as incorporating humans into the mix - let's take a minute to remember the smart kettle. We therefore have to ask whether proprietary protocols and networks will ever make a resurgence, or have they had their day? We know which side we're rooting for.