The discussion in https://news.ycombinator.com/item?id=17690815 is meaningful. There is, apparently, some disagreement about how the protocol versioning should be interpreted: zx2c4 (J.Donenfeld, wg creator) refers to the "v1" string used in the construction as the version identifier; tptacek refers to the primitives and the separator strings; I consider the whole thing.
Regardless, it is clear that there are numerous ways that can be backward compatible to extend wireguard into v2. IIUC, the deliberate design decision is that "we are not baking any specific one-true-way". It's not "not preparing for the inevitability", it's "the way protocol agility has been done so far has failed, we defer this decision closer to the time we need it".
Thanks for the pointer. I couldn't find any (semi-)official information about this and seeing that the developers indeed care about this puts my concerns at ease to some extent.
Regardless, it is clear that there are numerous ways that can be backward compatible to extend wireguard into v2. IIUC, the deliberate design decision is that "we are not baking any specific one-true-way". It's not "not preparing for the inevitability", it's "the way protocol agility has been done so far has failed, we defer this decision closer to the time we need it".