Depends on how many people use it, footer links are considered the least valuable.
However its like a long-term investment. Even if one site makes it big using your template, you can get lucky.
I won't comment on Serps as many factors go into it, including niche, keywords and so on.
Footer links are sitewide so you will get a very large number of backlinks from even a single site.
e.g. If 100 people use your template, each has an average of 1000 indexed pages. Then you get 1000x100, i.e. 100,000 backlinks.
However, make sure you encode the footer.