Bornakk posted on the General Discussion Forums this afternoon that there will be maintenance tomorrow on all realms from 3:00 a.m. PDT until 11:00 a.m. PDT. Additionally, the forums themselves will be undergoing maintenance from 5:00 a.m. PDT until 8:00 a.m. PDT. You will not be able to log in to the forums, but you will be able to read them.
Patch 2.4.2 was announced last week and is on the PTR right now. However, it is unlikely that the patch will come tomorrow. The PTR phase of minor patches almost always lasts two weeks. Of course with that said, I'm sure I'll be eating my words tomorrow as 2.4.2 goes live. We'll all just have to stay tuned and find out!