Object enablers are related to the application, not to the format. So you have to install 2013-specific enablers for AutoCAD 2013. They can coexist with your 2012-enablers. Get the latest OE at www.autodesk.com/oe
As noted above, OEs are for the most part there to enable access to verticals content from AutoCAD variants like Civil, ARCH and more.
Word of caution: R2013, with or without enablers, will upgrade those AEC custom objects to a newer format, thus rendering them useless as editable AEC Custom objects in 2012 or lower versions of those vertical variants.
So... if you share files with folks expecting their CIVIL or MEP or ARCHITECTURE files back 100% intact and editable in their 2012 or lower versions, you will pretty much ruin the DWG files for them by opening and saving in R2013.
Do you truly know why you need and have OEs installed? Do your partners know you plan on touching their files with 2013? Time to consult before you leap, or someone is going to have to recreate every file you touch in 2013 from scratch (and pay for it).
We are stayng with 2012, so it won't be us that will be using 2013.
I understand the downsides to object enablers.
I asked the question about 2013 object enablers, because there will come a day that we will get a drawing saved by Civl 3D 2013 or another 2013 vertical and wanted to know if we did not have the 2013 object enabler installed on our 2012 computers, will we see custom 2013 objects?