Present vs Future

There is a sign in Cali that reads "Together we build a better future." To me. this doesn't sound grammatically correct. Building a better future is a future action therefore it should be stated in the future tense. I think the sign should read "Together we'll build a better future." Many people have argued with me that the sign refers to the present. Even so, the sign should read "Together we're building a better future" right? I'm open for opinions here, thank you.