It is a complicated issue as it is with every large update. I don't know if they some problems like Bitcoin and Bitcoin Cash back then? But I would not know why that could be the case.
Whatever but these updates are probably discussed in the slightest detail and I am sure there is no consensus all the time between them. Especially if you consider that the development individually has money at stake, which is good for the community but also leads to discussions because all of those brilliant minds on the Ethereum development team has their own opinion.
Not really a problem but a fork happened in the past. The original Ethereum back then was ETC and then the fork was named ETH which is now Ethereum, cmiiw if some experts find my explanation to be wrong.
But such update shouldn't really be hasten but it's also been a long time since they've promised that update. What's next then? when we're near to said date then they'll extend again? no one knows.
Yes but we also don't know their hierarchies and decision processes. What happens if they fundamentally disagree on something before the roll out? Maybe hat delays the whole process by a lot but they might not necessarily share any inside arguments with the public. Hopefully we will get the update and its promised effects rather sooner than later.