The way that Ruckus are moving is towards the SZ platform, as they are slowly merging the ZD platform funtionality, but I cant see the ZD's being marked for EOL just yet as they still have a place in the market in my eyes.
In regards to DPSK, it is a given that this will make its way to the SZ platform, but in terms of timeline I am unsure.
The only real thing that sets the SZ100 apart from the ZD's are the interfaces, of which you get 2 models on the SZ100:
- 1GE Model: 4 Gigabit Ethernet ports
- 10GE Model: 2 x 10Gigabit Ethernet ports and 4 Gigabit Ethernet Ports
If you are tunnelling your traffic back and your net capacity exceeds 1 Gigabit then you might need a SZ as all you get with the ZD's are 1 Gigabit.