After the CUCV series there was the CUCVII which ran from around 1996-2001ish. GM Defense made them and made every model CUCVII that was equivalent to the regular CUCV. I own/owned 3 CUCVII Tahoe models and love them. FMVSS compliant (no state registration issues), AC, overdrive, and surround sound. All of that came stock.
There were CUCVIII models that lasted for a very short window of time after the GMT400 style ended, but was subsequently replaced by LSSVs which are still produced today.
The issue you and everyone else will run into is actually finding one of the vehicles I mentioned. It took me years to find my CUCVIIs. The reason is because of production numbers. Around 80,000 CUCVs were produced whereas around 800 CUCV II vehicles were purchased by the US military for continental US use, and around 3,000 CUCVIIs went overseas. But all that said, around 3 or 5 will pop up for sale every year.
LSSVs are interesting because they've been produced for around 15 years with very few released to the public. Most all that are in private hands came from state or county level surplus auctions. The intention of an LSSV is different than the original CUCV, and combined with the low production numbers, that is why few have been released. I do not know how many have been produced, but if you average the numbers from the last three years budget from the US Navy it comes to about 70 per year, so around 1,000 have been produced.
The original CUCVs were designed as placeholders until the HMMWV came into full production and were subsequently surplused afterwards. The LSSV was designed from the beginning to be used in supportive roles and was planned for long term use. That is why most that have been surplused from the federal level to companies like GovPlanet are in terrible condition; they were used until "beyond economical retention."
...what is the next civilized (streetable) size of military SUV we'll get, if ever?
Probably none. Unless some new military support vehicle comes out in a large volume like the CUCV, you will never see anything comparable again.