Wikia Staff are presently working on a major overhaul to articles on all Wikia wikis, including The Sims Wiki. This change has not been well-advertised, and has so far received only a single staff blog post about it. But, based on the examples created so far, the changes appear to be extensive. No doubt this will have a significant impact on anyone reading or editing the wiki.
The right rail is being eliminated, and all modules currently on the right rail will be eliminated or relocated to within the content space itself. For example, the "Must Watch Videos" module is relocated to within the content space, and acts as a separator between sections.
The size of the content space is being changed again. The current width for the content space is variable between a minimum of about 700px, to a maximum of 1250px, depending on the size of the screen that is used to view it. The new space will have a variable width between 768px and 1150px. On top of this, the elimination of the right rail means the content space in centered on screen. For readers/editors with a 1920x1080 monitor, that results in 670px of wasted space on either side of the content space - over a third of the total space on screen.
Font sizes are being increased from the current standard, and scale in size according to the size of the display. On large displays, the letters are significantly larger than before and appear to be bolded. This has the added effect of reducing the number of characters that can fit on each line, making the pages longer than they currently are.
"Recommended content" (i.e. links to stuff on other Wikis, currently found in the right rail) will be given a spot directly below the content space
Wiki navigation is being updated. It will still be a drop-down menu, but will eliminate one of the rows of tabs in exchange for menus that can pop-out of the dropdown itself. The size of the wiki's wordmark is also affected.
See it for yourself
You can see how these changes will look right now by visiting the two wikis where this is being tested - Tardis Data Core and American Horror Story Wiki. It appears that this change so far is only on content pages and does not (yet) affect the main page, so you'll have to browse to a content page on either wiki in order to see this first-hand.
Alternatively, you can view these changes on any wiki, including The Sims Wiki, by adding "?useskin=venus" to the end of any page's url. For example, click on the links I've provided below to view these changes on a few pages from The Sims Wiki:
Keep in mind that our articles and templates have not been optimized for the new layout, so there may be visual quirks in the pages above that will be resolved if/when the new layout is implemented.
So far there doesn't seem to be any firm date for when this layout will be rolled out Wikia-wide. It is unknown whether we will continue to be able to view/edit the wiki in the current "Oasis" style or in the classic MonoBook style (though I personally think it's unlikely they'll get rid of MonoBook). And of course, as this is a design currently under construction, some details are likely to change before it is rolled out and shortly thereafter.
If you have any feedback about the new design, be sure to leave it in the comments below, as well as on the staff blog, as well as through the "feedback" tab that can be found on content pages on the two test wikis.