In short: why will the little tags not die?

I just changed the tag "symplectic" from all 5 questions, and "symplectic geometry" from 1, to "sg.symplectic-geometry" which is more relevant mostly. After a couple of minutes the listed questions were gone, as I hoped. However, if I pretend to ask a question and tag it, the obsolete tags still come up as suggestions. Will this change? If it does not, we'll continue to have many little tags in questions, which is annoying.

On a side note, I wonder if a "symplectic-matrices" tag should be added, or possibly better a "symplectomorphism-group", for the one or two questions that were just about Sp(2n).

(I tried to search for this question on meta; if I've missed it somewhere, sorry.)

Also, in this case it is better to either flag them for moderator attention or to post a request on the tag merge thread on Meta. The moderators have the power to do this kind of clean up without bumping all the questions up to the front page.