It will most likely be available for download for the foreseeable future. What Chris means by "limited lifespan" is that support for XenForo 1.x is nearing the end. Right now, XenForo 1.x will only get bug fixes and security releases, no new features. Eventually XenForo 1.x will be declared End of Life and won't get any updates including bug fixes and security releases.
When XenForo 1.x is declared End of Life, they may remove all downloads for it.
Regarding the look, there are MANY themes available from high quality designers such as
ThemeHouse and
PixelExit, as well as many others.
As Chris has mentioned, its worth taking a look at the various 2.x styles in the Resource section.
https://xenforo.com/community/resources/categories/styles-2-x.45/