As a fan of Lords of Shadow as well as past Castlevania games, I honestly don't blame you or anyone else who feels that way. At this point what can't I say that has already been said since Lords reveal in 09 and it's release in 2010. All I can say is that the silver lining in all this is that Mirror of Fate and Lords of Shadow 2 are the final games in the reboot. So there is a possibility that IGA may return to pick up where he left off in the original canon. Or rather if he's up to do more Castlevania games but sadly that's not up to him anymore, It's ultimately up to Konami weather they want to continue outsourcing and rebooting Castlevania to western studios or not. We can just sit back and hope for the best in the long run.
It'll be really interesting to see what they do with the Castlevania series going forward.
From the sound of it, MercurySteam wants to go leave and do their own thing, and frankly, since MercurySteam isn't a subsidiary of Konami there isn't much Konami can do about that besides throwing money at them. I doubt Cox is going anywhere, though, as he is an employee of Konami and they can tell him to do whatever they want. Hopefully they'll let him go, since he has said he doesn't want to be "Mr. Castlevania", but that's, again, Konami's decision.
I really don't see Castlevania going back East to be in the cards at this point, at least not for major releases. Castlevania has always been more popular in the Western Hemisphere, and if anything that Western fanbase has only become more niche since the series got more and more Japanese. Lords of Shadow had some of the best sales the series has ever seen, so when MercurySteam drops it, I wouldn't be surprised to see Konami give it to another Western developer to continue what Lords of Shadow started. This gives me mixed feelings, since although I did really enjoy LoS, I've spent the last 15 or so years playing the increasingly stylized Metroidvanias, so all I can really do is wait and see what the series has in store for us.