Keep in mind if you are reading this thread, you are a WoW minority, most people(the bad ones in LFR) won't even know where the new raids are if they can't hit Control I. Some won't even know there is an expac until they get a log in error, yes it happens more than you think.
I see both sides of this argument. Both are valid
The raid train is coming, everyone either chooses to get on or chooses to get out of the way.
People choosing to get on the raid train don't want to be delayed because they are going somewhere in a hurry. Layovers aren't fun for most people.
The idea of not being "forced" to miss content in order to be raid ready asap is nice, but that is the entry price of competitive raiding. Which is a choice that every raider makes.
Some people choose to have kids, choose to take care of their grandparents, choose to go to work, and choose to sleep. These people have a responsibility they choose not to ignore.
Some of the lucky ones can choose to do all the above, more power to them.
Let's all look to Darkmoon Faire as an example, we have lots of people are going to it anyway even though it isn't fully open. Why? It's still something fun to do.
Right now, we have a lot of people playing wow, waiting for new content, DS released in patch 4.3 on December 13, we have had no new content for almost 6 months, and if we wait till everything is ready, up to possibly 4 more months of no new content.
There is no way to win this argument. If we do have to wait till October, everyone who bought an annual pass is gonna feel like they got jipped a little. Everyone who did not buy an annual pass is also gonna feel jipped a little.
People are going to complain either way, Blizzard should just do it. Give us some thing new to chew on. But be 100% certain there are raids in the wings ready to be released no later than 3 weeks after launch. Also, don't throw any nerfs for at least 3 months on any future raid tiers, then stick to the 3 month minimum.
Furthermore, don't nerf it, make it a buff, it just makes more sense in the lore of things. If Mr.+Mrs. Awesome shows up and all of a sudden every mob hits for less and has less health, why doesn't Mr.+Mrs Awesome just kill it for us? Makes more sense if Mr.+Mrs. Awesome shows up and throws us a buff and tells us good luck.
Stop rewarding slacker players who can't take the time to gear themselves properly and learn their class prior to raiding. It takes away from the epic feeling of raiding when Mr.+Mrs. Complacent shows up and doesn't know that they have to push more than 2 buttons to help their team (Had to put this in here some where)
For the raiders waiting to get on the MoP raid train, time is relevant, we are all in a layover, stuck at the Dragon Soul Raid train station, we can get on another train which goes a little out of the way, but we will be moving(metaphorically speaking). Take that extra time and have a main + 2-3 alts, or get a Monk raid ready when the gates are open. I get the idea of being world 1st, it is a thrill and has its prestige, but none of that is being taken away. Or we all wait at the Dragon Soul train station.... for up to 4 months.
Additionally, even with a 2-3 week delay the top raiding world 1st raiding guilds will still be able to put some distance very quickly between themselves and the rest of the raiding community. World 1sts are still on the table, and still between the same 10 or so top guilds, so don't sweat it.
For PVP, we kill each other because everyday starts and ends in "Y". Two to three weeks of mindless killing is not a ground breaking idea, lets go gank people collecting pets. World PVP has returned!!!
If Blizz does go through with this, they can actually come out with a small technical win of releasing more new content faster.
In the big scheme of things this is still a game, play to have fun however you choose.