I think it's highly unlikely. There may be other dual core Samsung phones with a physical keyboard but the are horrible to use and make the phone large and feel flimsy so I don't think we'll ever see on the the SGS[234].
I never type large volumes of text on my phone but I do have a small bluetooth keyboard that works perfectly and comes in useful if I have to do something like type a long email. If you type a lot of texts on the go and don't like an on screen keyboard, you will have to rule out the SGS2 and its successors but if you want if for occasional but lengthy typing sessions, get a bluetooth keyboard.