Possible to send an image from Preview app to Adobe Photoshop?
My recommendation isn't a keyboard shortcut, but an easy way to send files between applications. Simply grab your file's icon at the title bar (proxy icon) and drop it on the app's dock icon (doesn't matter if the application is closed or open):



Subsequently your app will open (launch if the app is closed) and open the given image. 



It works on all sorts of apps with all sorts of files. If you have several versions of Photoshop, simply drag it to the one you please. Hope it's useful!