Yep, you're right, mate. Around August-September last year, people started to get in touch with BO3 Mod Tools and concentrated their efforts in learning the new capabilities of Radiant and Assman and eventually port their pre-existing work/map ideas into the new tools. At the same time, WAW modding really started to slow down almost to a crawl, to the point the Releases section for WAW custom maps didn't have a new post for 5 months, except for comments in existing posts (chn's Der Berg is the most recent release, from 2 days ago, though). Even UGX itself directed their efforts to the new tools, and I suppose UGX Mod 1.1 for WAW development is paused or at least have very low priority because of that (this is an assumption, it could be right or wrong). Personally, I think that is was incredible for this community to even recieve new Mod Tools to begin with, given how ATVI and the COD Devs (IW and Treyarch) had given less and less support to mods in their games since MW2, to the point the Mod Tools arrived incomplete and were left that way (Black Ops 1) or they were nonexistant (MW3 and onwards until BO3); but, at the same time, it's really sad to think that WAW modding is getting closer to the end of the line than ever before.
I discovered that WAW modding was a thing in 2013 after playing Black Ops 2 Zombies almost daily (BO2 was my first Zombies game. Quite late, I know), and I remember quite clearly how amazed I was after seeing all those different and creative (sometimes silly and bloated with features) custom maps that people were coming up with, and having a blast playing them in my somewhat-average PC, trying to find all those obscure scripted Easter Eggs and get all the perks the map had to offer. Nowadays I don't play as much in general (regardless of platform, not a PC/console fanboy) because of University and the little time it leaves to me to do that, but I follow closely this community, and especially this forum because of the awesome contents its members are capable to create, and their collaborative spirit: there always were someone starting to get in grips with custom mapping who had questions, and there always were people willing to help them, ready to provide answers. The result were custom maps that rivaled, or even surpassed, Treyarch's quality, like Leviathan, The Swan, Ragnarok, Encampment, Clinic of Evil, Das Herrenhaus, Oil Rig, Project Contamination and many more.
All that said, I really hope Treyarch sticks to it's word and 100% completes the Mod Tools with all the community feedback they've recieved so far, and all the feedback they will recieve in the future. This community, as I said, really needed new, more modern tools to work with, as WAW' limits were pretty steep to overcome for a lot of modders and mappers, that's the reason why a lot of interesting maps/mods were cancelled. T4M mitigated this a bit, but not many people were too keen on using it, both in the mappers and users' side. That way, many old and new mappers will come/return to the scene and make their ideas a reality with the great capabilities of BO3's engine.
It'll be really sad when WAW finally has to ride into the sunset, but I'm convinced that the community still have works-in-progress to be completed and released in WAW, and I cannot wait for them to see the light of day. It'll be World at War' last hurrah, and I'll be there to play and enjoy it, just like the first day, to the very end.