I'm almost positive that you are right about Hoid switching it out for a regular Shardblade. I read through the Epilogue of tWoK last night and Taln's Honorblade is described as being long, narrow and like a spike. However, the blade that Dalinar summons in the confrontation with Amaram is described as being wider than most and "cleaver-like." We know that Wit's been collecting powers from the Cosmere, so I think it's safe to say that he was in Kholinar that night to get himself an Honorblade.