Making the long story short: if I download and install the new Xcode 4.2 Developer Preview on my Mac and start developing new iOS 5 apps, can I still using it for developing and releasing iOS 4.x apps?
I do not have the possibility to install two different versions of this platform right now. Probably someone amongst you has tried it and can answer.
The iOS 5 beta Release Notes link associated to the new Xcode version seems to be broken.
Thank you!
No, you can only submit to the app store with the official releases of the tools, not the betas.
See also Jano's comment above, on the dev forums it has been confirmed that you can't use the beta tools.
Unless you're chronically short on disc space, you can use disk tool to resize your current partition and do a new OS install on a second partition that you then install all the beta tools onto. (You can also do an OS install onto a removable firewire drive.)
I prefer to keep all the beta tools on a complete separate OS installation, as then there's no danger at all that I'll end up a state when I can't publish apps, and publishing apps is what makes me money.
来源：https://stackoverflow.com/questions/6265754/can-i-use-the-new-xcode-4-2-developer-preview-to-publish-regular-apps-now