Basem Emara has also written a module to implement Newsletter Manager Pro in Sitefinity 3.6/7
It's in the marketplace http://www.sitefinity.com/marketplace/modules/newsletter-pro-module.aspx
I haven't tried it but worth looking at.
I guess Telerik have held off committing to a newsletter module in 4.0 because it's debatable whether it's worthwhile writing this functionality from scratch. As they have done with Analytics, using Google as the backend and just writing an interface on top looks like a great solution.
I hope that with the flexibility of 4.x and the growing marketplace around Sitefinity we will see the option to integrate lots of different products, both Telerik and 3rd party to satisfy common project requirements.