This is an intriguing thread. It is an ambitious idea that would benefit both fliers and (most) developers, but as others have pointed out, there is not enough market demand (low customers/revenue) and too many layers of complexity (technical requirements) for an easy answer that would meet all the different price/performance objectives.
A lot of the technical considerations have been discussed, but a few big ones haven't. To have a "standard" I think you would need to align on three layers of the stack: 1) the frequency ranges (e.g., 900 Mhz vs. 433 Mhz, etc.). 2) the radio type (FSK, ASK, Lora, etc.) 3) the software protocol and speeds (NMEA, APRS, New Standard?, etc.).
If your design objective was the lowest cost standard then you would likely design to a 900Mhz FSK NMEA subset, but your range and breadth of data would be limited. On the other end of the spectrum, if you wanted something more full featured you might use a mesh network Lora radio in Amateur bands (70cm/433Mhz) with a protocol that supported both GPS and other telemetry data. Building devices that support a broad range would get a lot more expensive.
In my thought experiment, I considered that a club could build a "universal base station" with multiple radios that could read/receive signal and protocols from all the top trackers and then "repeat them" to club handheld trackers. That would be an interesting way to create a "universal" receiver and would take the immediate pressure off the manufactures to standardize, although it doesn't align incentives with developers, as it cuts out half (or more) of their revenue on the receiver side. That proprietary "universal" base station/repeater would also be very expensive - defeating the purpose.
I could see a path to a standard if two or more developers got together, likely that share similar radios/frequencies, and decided on offering an alternate protocol -- like a switch for basic (standard) vs. normal protocol. This would be analogous to a stereo that outputs in Dolby 8.1 normally, but can be switched to just output in stereo. The basic mode would allow for compatibility with their universal trackers (or others to come). They would have the first mover advantage, but would also have more work. I think this path of cooperation is more realistic than Tripoli publishing a standard and hoping the developers will follow.
-Mike