Can of worms...
OK, so they are throwing out the old buggy code and writing some new
buggy code, good.
But they aren't actually throwing Trident out, so they still have to maintain it.
The next question is, are they:
i) Incuding Trident as standard and activating it automatically when a
broken IE-specific site is encountered. -> The detection code is unlikely to ever work properly, and will usually cause subtle and non-repeatable failures.
ii) Make Trident an option -> Microsoft gets a new revenue stream, IT managers get a headache of deciding whether to use it, and how to tell users when they should switch, if they do.
Final question, are they insane?