well, yes, but I was thinking more of where the href points to, in my opinion that's would be the Hashtag itself.
I don't remember seeing anywhere that it should be a Link not an Object.
For my projects hashtags are still Objects with an empty type, as at the point I wrote the vocabulary data types, there was no "Hashtag" type value yet, and I think it's still not there in the published versions of the Activity Vocabulary spec.