Yes I think GNX 3000 is the latest.
GNX 3000 has a vast arrangement of amp modeling and cab modeling (much more than GNX 4) but does not have the looper or on-board multitrack recorder which GNX 4 does have.
GNX 3000 does have computer software that comes with it where you can record to your PC on the fly and playback on the fly, but to set up a loop recording you have to use the mouse so loop playback is possible on the fly but only after you set it up with the mouse which is not on the fly.
Back to the modeling;
You have 65 user presets for for your entire 5 stomp board for which each preset is capable of two different amp/cabs on the fly (stomp). You can choose between two factory preset amps and then choose two different factory preset cabs.....or you can hyper model your own amps and cabs (save them too which is saved under a separate memory bank) starting from any factory preset and then changing the resonant frequency/bass/mid/high of the cabs and then changing the tone/gain of the amps along with changing the pickup for the amp (yes it also models pickups and does a great job making your single sound like a double humbucker). I think there are about 30 different amps and cabs to choose from.
The GNX 3000 also has the Univibe stompbox and Digitech went all out on this as they bear the Univbe trademark so they must have purchased the licence....but the proof is in how it sounds which is fantastic and it is "totally" tweakable. GNX 4 does not have this.
The GNX 3000 also has the best Rotary sound I have ever heard besides a real Leslie. Digitech also went all out on this stomp as the Rotary sound is totally tweakable too, phase, chorus, tremolo, vibrato, top speaker, bottom speaker, and different speed for top and bottom speaker (not preset speeds or sounds....analog controls). It is amazing! GNX 4 does not have this.
The panning is totally awesome. The GNX 3000 will auto pan any function and also pan by expresion pedal any function.....need I say more.....you can not begin to imagine all the things that can really be done with that feature.....I am still experimenting with it. I do not know if GNX 4 has this or not.
Trigger phaser, trigger waw, trigger flange, auto waw, auto flange, auto phase, expresion pedal flange, expresion pedal phase, and of course expresion pedal waw.......you can also use the expresion pedal for up to there different functions simultaneously but I haven't got that far yet. Synth Talk (using the mic which plugs into the low z input on the GNX, ya ya, chorus with several kinds, tremolo but not as good as my diy lune, echo options out the ass, distortion....real good sounding distortion options and you can auto pan the distortion too either the level and or across stereo mixing clean in and out etc. This short paragraph is just the beginning, no way to say it all.
The best thing about the GNX 3000 is all the factory presets sound so damn good and usable (135 not including the user presets...so 195 total). I have had other work stations and the factory presets sound so abrupt and would never be used in a song, just an exhibition of how far you can push the thing to sound outrageous.
Last but most important, the factory acoustic guitar setting makes my Jackson sound just like a classical acoustic guitar with nylon strings..........unbelievable I know.......but true.
The worst thing about the GNX 3000, it takes a long time working with it before you can remember the navigation paths to get it to do what you want......it is is complex work station.....but I can now walk right in seconds and tweak any setting just as quickly as adjusting my Tremuls Lune or my BOSS OD2. Practice makes the difference for any musical endever which you should know to be true.
Good luck and apologies for late reply.