Occasionally, we have people expressing confusion about loss of Followers. I updated my template, and I lost my Followers! If you only update your template and nothing else, your blog should still have its Followers. You may lose various gadgets from the template, when you make changes - but even if the Followers gadget is lost, the existing Followers continue. Just look at the Followers community, from your dashboard, and you'll see the Followers.
What Blogger won't tell you