Going the other way the speed limit is 100, with an 80km/h advsory speed through the interchange -- much like this will be once the rest of the freeway networks open.
The reason that I posted all of those examples is that I found it annoying that you purported that there was somehow something wrong with how speed limit drop was managed without:
(a) actually seeing the interchange configuration; or
(b) being a traffic engineer.
I've not designed a freeway terminus either, but I've seen enough of them to know that what has been designed here is within the realm or normalcy in both Ontario and other locales in North America.
My entire point from the beginning was that I thought it was a little ridiculous for the limit to drop 3 kilometres in advance. It was explained to me that this was due to the end of the freeway,
plus the curve for the directional-T interchange (see cbeach40's most recent reply on 10 Jan). I thought that was kind of silly, since advisory limits were supposed to be used for curves, and lowering the limit that far in advance might cause a differential in speeds (some continuing at 100, some lowering to 80). Even you stated above that "the ramps that have opened as part of the 407 extension have been consistently some of the fastest freeway to freeway ramps in Ontario".
I may not have stated it directly, but I would prefer to see the limit remain 100 until about a kilometre before Taunton Road, with an advisory 80 limit through that curve (so an advisory 80 limit, followed by a drop to a limit of 80). I know it seems like splitting hairs, but I don't like freeways with a posted speed so far below the design speed. I totally understand lowering a limit before the end of a freeway, but that far in advance just isn't necessary. Some might even view it as a speed trap.
The one freeway terminus near me that is involved in an extension project, the WA-167 extension from Puyallup to Tacoma, has no limit drop before ending at a half-SPUI. There's no curves or loops involved, granted, but even if there were, the limit wouldn't drop 1.8 miles back. One limit drop I know of off-hand is a drop from 100 to 70 about a mile before the freeway's terminus (WA-512 approaching I-5). It's universally ignored even at just a mile long.