Authorize.Net recently announced that they will be updating their API endpoints in a way that allows them to take advantage of Akamai. For the moment, this has no impact on existing s2Member installations.
What is s2Member going to do, if anything?
Our plan for the short-term is to do nothing, as these new endpoints could potentially cause problems with some web hosts that have already whitelisted Authorize.Net's API. So for us to change it now, when the change was just introduced so recently, would be a bad move in our opinion. Instead, we will continue to test this and prepare for a transition in the future.
Authorize.Net writes...
Phase Two (June 2016) — We will automatically direct all of our existing transaction processing URLs to connect through Akamai in June of 2016. After this change, all transaction URLs will connect to Authorize.Net through Akamai.
What we take from this is that Authorize.Net is going to use Akamai for all of their existing endpoints too. Thus, your installation of s2Member will be updated automatically once this comes out of the public beta so-to-speak (around June 2016); i.e., the updates that Authorize.Net completes will automatically move you to Akamai anyway; even without us changing anything in the s2Member software.
Updates to follow...
We will keep monitoring their progress on this, and should we decide to update the API endpoints in s2Member ahead of the June 2016 transition, we will post this as part of a formal maintenance release and document that change in our changelog.