I don't think the RGTs did as well as they hoped because of the price, and as others have mentioned, neck-thru + trem didn't seem to fill the intended niche.
Also, the RGTs didn't have any of the beloved wizard profiles - instead, they had the ultra profile, which is chunkier and feels more traditional. While some people loved the profile (I've seen several ESP players love it), it seemed to throw off many RG enthusiasts, as most are used to the wizard profiles (which is a huge reason some players strictly play RGs).
Lastly, I believe most RG enthusiasts prefer bolt on necks. Neither construction is better than the other, it's more about the guitar as a whole. Personally, I had an RGT320Q-RBB for a while, that I let go because I wasn't digging the neck profile and tone. It was my first neck-thru RG, and I wasn't really a fan of the tone. I swapped the stock pups for Dimarzio D-activators and tuned it to D standard. Although it sounded tight and aggressive, it also sounded too bright and thin for my liking. The wings were mahogany, but the pickups sat in maple, which is why I think it was overly bright - that in combination of having a trem. It also had a "quacky" midrange that I could not dial out, and didn't have that problem with D-activators in my RGA.
I also wonder why they haven't made more MIJ RGAs over the years. They seemed to have been popular... Starting with the RGA321s & RGA121s, then the trem equipped RGA420Zs & RGA220Zs. I have a 321 and 420z and they are super nice, pretty similar to the RG3120 in terms of quality. My only complaint with the MIJ RGAs of the past is that the flamed tops have been super inconsistent - especially the RGA321s - I've seen some with absolutely no flame and some with really nice flame, and everything in between... But mostly very subtle flame unfortunately.
I've seen spot model J Custom RGAs pop up, and the newly listed RGA prestige uppercut, but they're ridiculously priced. Other than that, we've seen the return of the RGA series in the iron label line... which sucks for people who are shopping for MIJ. Best bet for those people is to look for a used 321/121 (fixed bridge) or 220z/420z (trems).
Regular RGA prestige's might make a come back, but it's probably a long shot. I don't think we'll see the return of RGTs, but if we do, I think it'd be a fixed bridge version (tight end R would be cool, like on RGDs). Ibanez knows their RG series sells the best, so I guess they've decided years ago to stick with that for the most part in the prestige line. Times are changing though and they have to keep up competition with other brands!
Here's my RGA420z