I think you're being way too pessimistic. I've been thinking about why Fallout 4 was so meagre, despite some four years with Skyrim DLC:s as the only apparent distraction. One explanation could be that they were working on both these unannounced projects already then, in parallell with Fallout. That Giant Monster News thing Zenimax have trademarked was first filed for in 2009. Starfield in 2013. If we allow a stretch and guess both are BGS games (it's not unlikely - they've always trademarked their titles in the past at the beginning of the development cycle, and GMN and Starfield are the only unannounced game patents Zenimax have currently) we could very well see GMN in 2017, in which case I'd also guess Starfield lands in 2019. That would leave 2022 a pretty reasonable, even conservative perhaps, guess for TES VI - which could also be why Hines said he'd joked about the "22/22/22" release date with Howard. Had there been enough months it could very well have been about when we'd see it.
Note also that they've begun talking about TES VI now all of a sudden just as Fallout 4's DLCs have been wrapped up. That could have freed up enough people to make room for starting coding TES VI as soon as people are back from the holidays in August. If they rather focus on the two they already have going, well then I bet they'd start as soon as the first of them hits the shelves - which I insist could very well be already in 2017 as per the above. Either way, from the info we have currently release dates past 2022 seems like longshots, and production starts are virtually out of the question from my way of seeing things. Keep in mind also that they're two studios now, which could even speed things up to a quicker cadence than we're used to, assuming Montreal isn't kept exclusively for remasters and mobile stuff. Although I think two years would be about the minimum in order for them not to begin competing with themselves.