Updating firmware on Linux Wyse devices

I help support an environment with multiple and mix of Linux Wyse (LWT) nad Wyse ThinOS (WTOS) devices.  I've noticed that there have been no new firmware updates for the D50D, Z50D, X50m and C50 LE Wyse devices have been made available for quite some time. 

Can anyone tell me whether there are equivalent firmware update for these devices (D50D, Z50D, X50m and C50 LE) now that Dell is using names like 5010, 7010, etc. to identify it newer products?

Any information or pointers will be appreciated.