If you don't have a back up of your Blogger posts, that means you will have to start publishing new posts after moving to WordPress but your readers will still be able to find you.
This is not the case if you don't have a custom domain and Blogger deletes your blog.
If you are using .blogspot address and Blogger deletes your blog, you will have to use a new web address if you decide to move to WordPress. You cannot use .blogspot address on WordPress and Blogger will not even allow you to set up a new Blogger blog with the .blogspot address of the deleted blog.
This means your blog readers will not be able to find you as they will keep seeing "Blog Not Found" anytime they visit your blog till Blogger re-instates the blog. What if Blogger decides not to restore your blog?
So, if you are still using .blogspot.com address, is it not wise for you to to change to .com today?
You can read how to set up a Blogger custom domain or you can pay me to get it done for you within 24 hours (You will get free custom email).
Remember to always back up your Blogger blog.