The answer appears to be until 7/31
Small Business Server L&SA to be removed from the August Price list « Debbie A: Looking at Licensing:
At that time while you can still buy SBS 2011, you can’t buy SA on it. Keep in mind that while the SA fulfillment offer says one copy of Windows Server 2012, that’s one copy of Windows Server that gives you a two servers installed in a hyperV parent right. So a 1+2 right not the old 1+1 right. Two instances of Windows Server + Exchange + Exchange cals + Windows Cals, + purchasing RD cals to give you remote desktop rights, means that a SBS like solution could be deployed with your SA make good pieces. Yes not the price advantage of SBS, but for those folks in that no mans land above 25 users there is the ability to grow beyond 25 in essentials (top limit unknown at this time) as well. In case you missed reading that in the original blog post.
“Additionally, Essentials can grow with the needs of your business over time; you can purchase and convert to Windows Server 2012 Standard, removing the maximum user and device limits while retaining all your data and configuration settings as well as the unique value-add features that Essentials provides.”
I know this is a lot ot digest and think about and for those wanting to add SA to SBS 2011 standard you don’t (apparently) have too much time to do it in.