I recently searched the remaining five numbers on EveryMac... None of them pop up yet (to confirm that the search function works, I searched A2159, the one we know is out, and the 2019 low-end 13" MBP popped up as expected).
I am very suspicious that A2158 is our friend the 16" MBP (this is somewhat more than a guess - the two MBPs are often, but not always, a pair of related A numbers). The other possibility is that A2158 is an even closer relative of the 13" than that (a new upper end 13" with a scissor keyboard or a 15" refresh, again with a scissor keyboard). In this case, A2147 is probably the 16" (if A2158 is a 15" refresh, the 16" is a new "super-pro model" well above the 15", since they wouldn't refresh the 15" only to discontinue it a year later.
I don't think the 13" or 15" refresh scenario is terribly likely, because it's a lot of MBPs in a year - remember that the upper-end 13" and the 15" are quite recent - they were last updated in May of this year. The only reason to do that would be if they were really desperate to ditch the butterfly keyboard. More likely, A2158 is the 16", which will come out in one or two high-end configurations this fall, with lower-end configurations and a 13" or 14" version to follow next year.
Completely guessing, A2179 and A2182 are two cellular versions of something small and light (different bands). Whether or not they call it a 12" MacBook, that's what it's likely to be the successor to. A2251 is the same thing without the cellular modem. That leaves A2147, which might be something big and thin (15" MacBook or 15" MacBook Air). The other way around is also possible (A2179, A2182 and A2251 are all the "something big and thin", which has the cellular option, while A2147 is tiny, light and non-cellular.
Right now, getting a 15" screen on an Apple laptop means paying $2299 or more for a 4 lb, 15" machine with a mobile workstation CPU and a (lower-end or midrange) dedicated GPU. That's expensive, although not when you consider how many cores it can have. It's also not especially light for a 15" Ultrabook (although it's very light for an 8-core machine with a dedicated GPU).
With a lot of compromises, LG has gotten a 15" Ultrabook just under 2.5 lbs. There are a number of them in the ~3 lb range. Apple might be interested in this market - how about a 15" machine around 3 lbs, with some 15w Ice Lake chip and iGPU only? What if it started at $1699 or $1799 (8/256 or 16/256)? This neatly separates the "i want a big-screen Mac notebook" justification for the 15" MBP from the "I want the power" justification for it.
It also allows Apple to both back off a bit on the thin and light design of the 15" (16"?) MBP and to raise the base configuration (and the price with it). If there's another big-screen notebook, the 256 GB SSD on the base MBP is no longer needed - that $2299 configuration goes up a bit in price, but gets 512 GB instead. Similarly, the the $2799 model becomes a 32/1 TB configuration (while becoming more expensive, but perhaps not as much as buying those upgrades). I suspect the 16" gets closer to 4.5 lbs - still thin and light, but not as thin and light as its predecessor, allowing better cooling and perhaps a larger battery along with the scissor keyboard. For those who really want the lightest possible big-screen Mac, there's the 15" MacBook.
