There is no active work presently to get kgdboe merged to the mainline. Kgdboe is viewed as an unstable connection type in its current design.
For example, with IRQ preemption there is no safe way to share the ethernet hardware. There are few if any ethernet drivers that have a completely robust NET POLL API implementation. The remaining problem is that the amount of code which cannot be debugged with kgdboe is much larger than when using the dbgp or serial based I/O driver.
There are several proposals in existence about how to change the design and at the point that someone picks up one of those to carry forward you would also have the capability to run kdb over the kgdboe I/O driver.