@Wyote: if anything, the fact that it's all connected in some grand way that Sherlock is
vaguely aware of might be a lower-order Ni rather than a dominant one.
Sure, subliminally maybe it's all tied to his relation to Eurus/going towards his encounter with her. And sure, maybe he's on some level aware of it.
But basically, I see this as a TiSe type that, like wolly says, meets things spontaneously (in fact, Sherlock literally tells Mycroft when London is on terror-alert in the episode where he reveals he's not dead to John.. that the answer will be in some random detail that he's just got to keep his eyes open for), figures them out as he goes, vaguely aware of a sense in which it's all interconnected and heading in some direction.
I also see this as (in a parallel way) a 7 with an inner 5 conflict lying behind. His standard personality is stimulation-seeking, constantly bored, and so on. However, all this is driven by a sense of scarcity/lacking that began perhaps when he wasn't up to the competence to save his childhood friend from the well. The integration point is often presented as a sort of deeper inner self, a reaction to which produces the neurotic needs of the core type.
Frequently enneagram/the Jungian functions (while not identical systems or trivially translatable into one another) interplay in such a "natural" way.