If Season 10 ends November 15th, does that mean that patch 4.3 is necessarily a week behind?
Possibly. The length of time between seasons has varied. Using the Arena season dates from WoWWiki, we get:
- S1-S2: 1 day.
- S2-S3: 2 days.
- S3-S4: 1 day.
- S4-S5: 63 days. This period was between BC and Wrath.
- S5-S6: 7 days.
- S6-S7: 7 days.
- S7-S8: 14 days. Opening of Crimson Hall wing in ICC.
- S8-S9: 63 days. This period was between Wrath and Cataclsym.
- S9-S10: 7 days.
The BC data doesn’t really count; it’s obviously a different kind of season transition now. The inter-expansion periods don’t count, either, because there’s such a huge gap (9 weeks!) and we’re not between expansions. So that leaves us with 4 Arena Season transitions of the modern era.
It’s correct to say that there is normally a week between Arena Seasons. Three out of four have done so, and I think it’s Blizzard’s intention to continue to only have a week between seasons.
But it’s not correct to say that there is always a week between Arena Seasons.
Cynwise's Warcraft Manual 
My bad for phrasing it as always. š Was trying to guess how many weeks of full 25m Firelands (vs. 10m off-night) I had left assuming earliest patch drop date, as size affects the Essences count I get for the legendary.
@pon: I was honestly curious about it when you asked. I was surprised at how long the pauses between expansions were, and I’d forgotten the whole Crimson Wing delay. Just thought I’d pass it along! š
@Cyn Oh, it’s appreciated! I should have looked it up myself, but I’m a lazy bum. =P