I hope not :(
Though my guess is more of he's going to the Monarch's side with the intent of revenge
But I want him to remain sunny :(((
Well, I wonder about revenge... but I really am not of the opinion that he could remain as sunny as before after experiencing what he's going to be put through after this chapter ╮(￣▽￣)╭ ...more like he's just gonna be broken (and no, not the good kind of broken)
Don't let this get you down though. This is just me influenced by all the grim and dark shit out here... We'll just have to wait for the next chapters to see what'll become of poor Luca.
...for whatever reason (cause I've seen it on many other anime/manga/movies even though I don't understand it myself), this makes Luca break bad and defect to Monarch's side... like he still hates Monarch but his view on life changes and now he agrees with whatever Monarch believes in... or something like that.
Well, kidding~ (or not ¬‿¬)