Vaadin 7.1 beta1 has been delayed due to some open issues (see the corresponding link to our issue tracker at the bottom of the roadmap page) that need to be fixed before the beta release. Some of the fixes listed there are under review while some others are still to be done. We try to get it out as soon as possible - perhaps already later this week.
There will be an announcement about the beta when it is out, and most likely also the download page will offer it as an option. The Maven/Ivy version number will be in the announcement as well as on the download page (most likely “7.1.0.beta1”).
Once the beta is out, I don’t think you’ll miss it if you follow the main page on vaadin.com or Vaadin Twitter account or Vaadin blog or Vaadin forum or the download page…