At this point there's really no reason to think it will be AMOLED. We already know HTC has a 4.3" TFT they are currently using. They also have a 3.7" AMOLED that has made appearances in every recent phone that uses that screen technology. There's no reason they couldn't include a larger AMOLED (there are even 4.3" WVGA AMOLEDs on the market), but it's pretty unlikely that they suddenly switched production to include different screens. It would also be a pretty big coincidence if they were to use a AMOLED that happened to be 4.3" just like the current TFT they are using in that size.
Plus, there's the fact that
Sprint's developer site lists the screen as TFT...
