Forking causes more political issues. PHP is installed a lot of the time to handle what could be said are low quality code bases by hosting companies. There is still divide in the PHP community whether OOP has any place, even though I would say most( if my job shouts are to go by all ) now require it. Things have changed a lot in the last few years and in London good OOP, database and PHP skills are quite hard to find. This would probably leave most hosting companies to settle for the version that leaves it as it is. It will be hard to move to 6 as it is. Every hack solution posted on a forum that becomes the accepted answer could possibly be one step back, especially if it gets into an application that is widespread. This site is good as like PHPBuilder, there is a level of quality policing. Cuddles are only worth so much.
However, PHP mentality is currently about retaining backwards compatibility, so function renaming is certainly out of reach and isn't very practical for current PHP programmers. However, a fork-off of PHP with a more user-friendly library would be useful for those who just want something different. In fact, the current library of functions is something that is used to discredit PHP the most, in anti-PHP arguments. I'm not talking about changing the current language, because there are always people who, like you, like things the way they are.
I agree, languages evolve to fix problems that are re-occuring/tiring to handle in their domain. Often there are common problems that are language independant so need to be solved in a common fashion, so if there is an elegant solution already out there why not use it. The arguments for and against are already there if looked for.
Besides, if languages didn't borrow things from others then OOP would be dead and Java, PHP, C++ and C# wouldn't exist. I'm not saying I want to turn PHP into C++ or Java, but I'm saying that PHP could do with a library comparable to them. If you find that ridiculous, then I hope you aren't a part of the development of the PHP language.