Many fans, myself included, have been thinking of ways it's connected to the main series and thus be canonical, but the official word from Cox & his crew is that LoS is not canon.
But that's not what Dave said. The point he made is that it's not part of the
old (IGA) canon. It's not like IGA's story is the official one and this is fanfiction. For what we know, from now on Castlevania lore may be built on LoS' lore instead.
While the idea of throwing away 20 years of love and speculation scares me, IGA took the "canon" in some terrible, obscure places and ruined it at both extremes (LoI's was a terrible origins story, and the Soma games completely killed the story's ending).
I can very much see the need for a full reboot to rebuild the lore in a functional, enjoyable way. I've got some mixed feelings on some of the LoS events, but let's see how they move from here.