Sean, I'd also like to have some idea of when the next stable version of Scribus will be released but in the meantime you could try installing a copy of 1.5.0svn. (You might have to compile it yourself if you can't find an installation package - look at the bottom of this page
http://wiki.scribus.net/canvas/Download for more info, or do a web search for "Scribus 1.5.0SVN".) While it's not officially called a "stable" version there are quite a few people using it as their production software.
You just have to be aware that the software might change and if some features are altered significantly - or removed - then some documents created with it may not load properly in later versions. It is developmental after all.
If you only need the new features for single/short-term use and your installed copy works for you then that shouldn't be much of a problem. However, I personally wouldn't recommend basing any long-term projects on anything other then the current stable version.
Also in the meantime, have you considered using LaTeX for creating tables in a render frame? There are various web sites/pages -
http://truben.no/latex/table/ and
http://www.tablesgenerator.com/# are just two examples - where you can quickly design simple tables and copy the LaTeX commands to Scribus.
Formatting isn't up to much with these options - unless you really know LaTeX, which I don't - but they might be worth considering depending on your needs. (They also let you create all kinds of other tables from the same set-up so they might be worth bookmarking anyway in case you need something like them in the future.)
I hope some of this has helped.
Garry.