That’s very sad news. Part of the appeal is long term support. Two year is extremely short. That means that even Debian old-stable won’t be getting security backported anymore!
Kernel 4.14 and 4.19 are still supported right now upstream, which seems like an extreme maintenance burden. For Debian they might need to release an update to the next longterm release somewhere during their stable release (like Ubuntu already does with HWE) or suggest people use the backported update on oldstable.
The parties that want or need this kind of long term support are companies for the most part, which could very well crowdfund the personell to carry out these backports.The issue is not the absence of maintainers, it is the absence of awareness for crucial foundations by which these commercial entities live of.
I was already surprised by the amount of LTS kernel series. There’s currently six of them! I wondered how this is sustainable and it seems the answer is that it just isn’t.