I'll be sticking with trades right through to the end. I don't unnecessarily re-buy anything, so until my trades fall apart, no matter how pretty they may be, I'll never buy the Library Editions (which means I almost certainly will buy them eventually ((maybe 15 years from now)), because the trades certainly don't last forever, especially Strange Places, the Hellboy book I've read the most. It's dropping pages everywhere). I can't buy these hardcover original graphic novels (though I am severely tempted... I want to read the these stories!). No author notes, no sketchbooks? That's a major dealbreaker for me. I'll patiently wait for a better format. At the moment they just feel like a slightly longer hardcover version of the standard issues. Hopefully one day there will be a trade that fits nicely with the others, otherwise the OGN stories are just artificially separated from the whole. Everything has always been collected in the trades. I see no reason to mess with such a beautiful promise to the readers.
As far as I can see, the only reason the OGNs exist is to make them visually distinct from the issues of Hellboy in Hell on the comic book shelves. I find it very unlikely there won't be a trade collection at some point in the future.