Bitcoin should never ever be forked like this unless there was a crisis. There is no imminent danger of hitting the block limit:
https://blockchain.info/charts/avg-block-sizeI bet 100 Bitcoins that if this Bitcoin XT fork was ever implemented it would cause huge problems and more forks would be needed to try and stabilize the blockchain. Worst case scenario is Bitcoin becomes unusable and loses all of its value.
Forking is a nuclear option when the blockchain is no longer functioning right, the only time a fork was needed was to fix a fork that Bitcoin QT developers accidentally created by releasing a faulty wallet.
Bitcoin is not like windows or an iphone, it doesn't need constant updates or any forks. If it's stable then it should never be changed again. The chart does tell us that a certain group tried to manipulate some numbers recently. However I do not believe that Bitcoin XT will cause "huge problems". It is essentially the same as Bitcoin Core but with just a few additional patches done by Gavin. I don't think that it will cause huge problems.
Forking is necessary. I'm not talking about the current situation. Your last part is incorrect. It should update whenever possible, including bugfixes and improvements. However we should only do forks if we reach consensus (not that easy).