A Dell press release on 4/23/2015 said the S4048-ON is shipping now.
This is a cousin of the S6000. Both are Broadcom Trident2 switches. The 6000 presents ports as 32 x QSFP+ while the 4048 presents as SFP+. ON in the part number means that the switch is sold with the Open Network Install Environment (ONIE). There is a datasheet. BCM56854
The Global NOC at IU used the S4048 as an ONIE Config example.
There is a blog with helpful advice for getting started.