Will iphone 4 support ios 8 after ios 7?

As ios 7 will not be available for iphone 3gs, will ios 8 will not be available on iphone 4?

Nobody can possibly know the answer to this. Nothing has been announced for iOS 8 and iOS 7 has not been released. In fact I think sharing that comparability information you just shared may be breaking the iOS 7 NDA, which is illegal.

Probably not, but at least iOS 7 will be supported. If you want to try iOS 7 early on your iPhone 4, you can get your UDID registered at http://www.instantudid.com/.It's $5, and then you can install the beta before everyone else.