The toblerone wish's exact wording was to make June "real, the will and direction of the fans." The word canon was not strictly used, so my presumption is that it falls under the "dubious canonicity" of post canon to some degree (to borrow Rose's terminology, a dubious truth value [the wording of the wish might mean June is properly canon *or* just appears in official hs media], near zero essentiality [nothing about homestuck proper changes as a result of June transitioning], but some definitely relevance ,[due to the toblerone, and eventually appearing in hsbc presumably].) Part of the problem is that Homestuck as a property is trying to undermine the idea of "canon" so there's not really a coherent answer to this