Microsoft is wise to let him go.
Once you have slowed down a horse (Nokia) by launching a parasite in its 4ss (Elop) , once you get on the horse's back it is not the parasite that will carry you.

In other words, when there is real work to be done, the last thing you need is Elop around.

Remember that he has killed the first enthusiastically acclaimed platform / phone prematurely in a year where the iPhone / Android tiredness was already setting in just by doing some smooth WP talking to a bunch of shareholders looking to cash in some bonuses during the Nokia to MS transaction.

Result is 4 years no progress (BB10 maybe a small exception) and ironically no WP reign either.

So true, just like they did not give a rats 4ss for Symbian, when it was all around.