Anecdotally, I lost .5% of my 13,000 followers in the last week or so. But I see a lot of people saying, "I'm here until after the election" so I suspect the exodus will continue.

Also, many of my friends -- especially those with some industry visibility -- are cautioning one another to NOT delete their accounts. Otherwise someone else can grab the account name and do icky things with the apparent identity. So I expect quite a few accounts to simply go dark (optionally with a pinned tweet, "find me at Whatever, now"), rather than pull the plug.