I am not 100% sure. Currently I haven't got time to install the "final" XE7, I still have the latest beta. There weren't any breaking changes so adding support will be fast, but we need to finish other stuff before we can release 6.5.
So as a 6.5 release is still some weeks away, I think we will be doing some 6.4.9 release before, which will add support for XE7 but not have all the other features in 6.5 (which is huge). In any case, as iOS 8 and OSX Yosemite are going to be released in approx a week,for the 6.5 release we will probably already have XE7 SP1 to support the newer ios/osx and we'll have to make a new release anyway.
Honestly, I can't understand who made the decision to release XE7 now, knowing that in a week there will be major iOS/OSX releases.
Although it would be great if XE7 was not released until IOS8, it allows us developers have a kickstart with XE7 so when IOS is released our software is ready. Therefore, it would be very good if you could release 6.4.9 which is compatible with XE7 as interim solution
The thing is, they can't add iOS support until it is released, because of NDAs. So they aren't really giving a kickstart to developers. iOS8 is the biggest iOS release since iOS2, there is a lot of new stuff that should be supported, and that can't be released until iOS8 is released. This isn't the same situation of XCode, where indeed you gain advantages using the beta.
And as a drawback, we need to test everything again in a couple of weeks in iOS8.
But well, I understand the situation, and we'll be making a FlexCel version available in the meantime. I'll try to have it for tomorrow.
FlexCel 6.5 with XE7 support has been published and are available in the website.