I really think all of the "no TBT directions" is because of licensing agreements surrounding the map data IP.
The quoted part of the Developer's License Agreement about no turn-by-turn directions is included because Apple is using Google Maps. Their usage agreement states that their maps cannot be used for turn-by-turn directions, so that bit falls down. A possible reason that Google Maps can't do the TBT is that Google is licensing their maps from Navteq. Google gets its maps cheap but for reference only. TBT directions would require higher licensing fees.
TomTom purchased map maker TeleAtlas in June of this year. And now since TomTom owns the maps they can do whatever they want with them. So TomTom is not breaking any licensing agreements because they will probably use their own map data, not Navteq+GoogleMaps.
Id like to see TomTom do it rather than Apple + Google because TomTom has experience. Its another area I don't thin Apple wants to get into. Part of Apple's strength is realizing where it is weak, and partnering with much stronger companies.
Having said that:
I really wouldn't be that surprised if google didn't put something like that together in the next maps update. Especially considering all of the effort and features that they have put into both the regular versions of google maps in the past year.
Google = more licensing fees. Whether they pass it on or not has yet to be seen.
Agreed, this is (should be) a HUGH feature of the iPhone and I'd like to see if FULLY integrated BY APPLE (and also think it should be standard - included free).
I think Apple might help out, but maybe not. And with the cost of licensing the map data (how much is an upgraded map DVD) it probably won't be "free". Nokia Maps TBT is not free. Garmin, TomTom, Telenav are also not free.
Why wouldn't you want this to come to fruition FROM

?
You'd
rather see a vendor do it?
Because they'd have to be the ones to do all the work, and incur associated costs. They'll leave it to someone who knows better.
If this is the case, Apple needs to loosen up. Tom Tom should sell the software for the jailbreakers at least!
As a large developer, I highly doubt TomTom will support the jailbreak scene. They'll go the legit route and sell in the App Store.