Great question! As someone working in industrial automation, I've been tracking these protocols closely. Here's what I'm seeing on actual factory floors:

MQTT is definitely gaining serious traction - it's become the workhorse for PLC-to-cloud integration. The lightweight publish-subscribe model is perfect for getting data from factory equipment up to the cloud efficiently. What's really driving adoption is the combination with Sparkplug B, which adds standardized topic namespaces and data formats. Companies are using MQTT gateways that read PLC data via Modbus or other protocols, then publish it to the cloud. The practical reality is that MQTT implementations are working well for monitoring, dashboards, and basic analytics.

OPC UA is also seeing solid adoption, but more for machine-to-machine communication within the factory rather than direct cloud integration. Its strength is the rich data modeling and built-in security - perfect for complex equipment communication. Many vendors are using OPC UA at the edge to expose machine data, then using MQTT to distribute that data to cloud systems. So OPC UA isn't hype, but it's often used alongside MQTT rather than replacing it.

TSN (Time Sensitive Networking) is the one that's still more hype than widespread substance for most factories. While the technology is maturing and showing impressive results in labs (sub-millisecond latencies), actual factory floor deployments are still limited to pilot projects and high-end applications. The manufacturing sector is the largest adopter so far, but it's mainly in advanced automation scenarios where deterministic communication is absolutely critical. For most PLC-to-cloud integration, standard Ethernet with QoS is still sufficient.

The practical reality I'm seeing: MQTT for cloud connectivity, OPC UA for rich machine data, and TSN for specialized real-time applications. Most factories are adopting a hybrid approach rather than betting everything on one protocol.