3 raid tiers and a strong possibility of a short filler raid
By that logic.
Vanilla had 7 tiers:
Molten Core.
BWL
AQ 20
AQ 40
ZG 20
Naxx
BWS 10
Strat 10
Burning Crusade had 9 tiers:
Karazhan
Grull's Lair
Magtheridon's Lair
Serpentshrine Caverns
Tempest Keep
Zul'aman
Hyjal Summit
Black Temple
Sunwell
Wrath of the Lich king had 8:
Naxxramas
Eye of Eternity
Obsidian Sanctum
VOA
Lulduar
Trial of the Crusader
Icecream Citadel
Ruby Sanctum
Cataclysm had 6:
Baradin Hold
Bastion of Twilight
Blackwing Descent
Throne of the Four Winds
Firelands
Dragon Soul
Pandaland (will) have 5:
Mogu'shan
HOF
TOES
TOTh
SOO
But that's not how tiers work. There can be multiple raids along a parallel tier or half tier (AQ 40 was 2.5, BC had 3 dungeons on t4, 2 t5, 3 t6)
Steve Irwin died the same way he lived. With animals in his heart.
I doubt we are going to have the last raiding tier of this expansion last as long as the previous ones. It's almost certainly going to last longer in my opinion, mainly for two reasons:
1. No matter how you view it, the last raiding tier of an expansion has to last somewhat more than previous tiers during the expansion, since it encompasses both the normal duration of the tier and the duration of the period where the tier is nerfed for some guilds to catch up. Right now there are guilds progressing in tier 14 in its nerfed state, while the others progress in tier 15. Come tier 16 some guilds will be progressing in tier 16 content while others will be finishing up tier 15. But in tier 16 there is no following tier to allow guilds to catch up. So the logical thing to do would be to add a period of time where tier 16 gets nerfed and let guilds that need the nerfs play. This is also hinted with the inclusion of the (in)famous unannounced special feature of Mists: being able to run older content as if it is current somehow. Why would they give players such a massive amount of content but not the time to enjoy it? Most probably in my opinion tier 16 will be extended so that guilds that need help in progressing in it will get it in the form of nerfs, while most of everyone else will play with the new special feature.
2. No matter how fast the developers work, there is no way to release a new expansion as fast as the current tier cycle makes some people think. A new expansion is a massive amount of content compared to patches, even major ones. Just testing would take a long time to carry out somewhat succesfully, and we don't even know anything about the expansion, much less have a beta testing date. Also the fact that Blizzcon is held in autumn and not the summer, and so late in autumn actually, where the new expansion is almost certainly going to be revealed, leads me to think we have a long way to go ahead of us before any 6.0s arrive.
This is something I would like to see, not specifically Kazzak but, if the next expansion is legion, we could get a final content patch after 5.4 that gives us the start of the legion invasion. Maybe some events and content based around it.
Unless they push out the next expansion faster than ever before, we're still looking at a near 1 year gap between SoO and the 2 year mark when they usually release the next expansion. A bridging patch can't just be a scourge invasion or even the Halion patch. It would need to be bigger in scope with a good amount of content to stave off that horrible year of nothing. Or of course get the next expansion out faster.
I believe a MOP will have 3 raid tiers total.
5.0/5.1 - MSV/TOES/HOF
5.2/5.3 - TOT
5.4/5.5 - SiegeOfOrg
IMHO we'll get 5.5 but not raid after SoG