Before discussing the question from the title, let me answer another one: Is this blog dead? Definitely no. Summer time distracted me a bit, but I'm hoping to get back to writing now :)
So it's more than half a year since I've concluded my series about NHibernate's mapping-by-code. The series is still surprisingly popular, there are quite a lot of hits from Google every day. I've also just reached 50 upvotes at Stack Overflow in a question about where to find some docs and examples for mapping-by-code. Thanks for this!
Quick googling for "mapping by code" and skimming through NHForge website convinced me that still there is nothing better available in the topic. Moreover, none of the bugs I've encountered half a year ago made any progress - all issues left unresolved and unassigned back then are in the same state right now. These facts are a bit sad, as I saw the mapping-by-code feature as quite revolutionary and shaping the future of NHibernate.
Well, and here comes the question - maybe there is no future? Maybe everything what is needed in the subject of object-relational mapping is already there and no development is needed? Ohloh stats notice some development in NHibernate project, but the pace is rather slowing down. No new releases are planned according to the roadmap on issue tracker. There are 25 issues classified as "Critical" unresolved, oldest waiting for more than 20 months by now. The development in a third-party ecosystem has already stopped - see the Ohloh graphs for NHibernate.Contrib or Fluent NHibernate, to name the most significant ones.
In my opinion, the reason for NHibernate's agony is simple. It was already discovered many times that applications nowadays are mostly web-based, read-intensive, not so data-centric and not consisting complicated data manipulation as few years ago. With the advent of mature NoSQL engines - free, easy to use and full of neat features - like RavenDB and - on the other side - with lightweight ORM-like tools like Dapper or Simple.Data, that cover at least 95% of ORM features needed to effectively handle newly-designed relational databases, we just don't need to use such a big and heavy tool like NHibernate.
Legacy databases are still a niche for NHibernate, for sure, but how many legacy databases that are not OR-mapped yet we still have out there? And for fresh developments, I'd say that unless you're designing some kind of specific data-driven application, it is more effective (both in terms of development effort and performance) to stick with either NoSQL or some lightweight ORM instead of NHibernate.
NHibernate is a great tool, but time goes by pretty quickly. The context of our work changes from year to year and even good tools some day must be superseded by better ones, that are more suitable for nowadays needs. And I think that day for heavy, multi-purpose ORM's like NHibernate has just come.