Or adding something like a firewire card which happens to be based on a PCIe to PCI bridge chip would also add a bus and therefore has the potential for names to shift arround.They are stable as long as the kernel and the hardware do not change too much; e.g. enabling the "other" graphics card in a hybrid setup sometimes adds a PCIe bus, so all names shift around.
The new scheme seems to have the same problem the original kernel scheme had but moved one level up. Instead of network names depending on the order in which the kernel enumerated network adaptors they now depend on the order in which the BIOS enumerated "PCI busses"* Is that an improvement over just letting the kernel assign names? is it an improvement over debian's scheme?
For servers the answer is probablly yes, servers often have a lot of network adaptors, adaptors may be replaced by maintinance personell who are different from those setting up the OS and the chances of people adding or removing hardware that creates extra PCI busses is pretty low.
For desktops on the other hand i'm inclined to belive the answer is no. Desktops rarely have more than one or two network adaptors but they are much more likely than servers to have things like graphics cards, firewire cards, serial cards etc added or removed which can mess with the PCI bus numbers.
* in quotes because on modern hardware a logical PCI bus may or may not represent a real PCI bus.