The important question is whether the RFID actually carries all of your information, or if it just carries an internal identifier of you that the scanning computer will need to look up in WDW's intranet in order to verify guest info or charge to the guest's account. The sane answer is the latter, but you never know.
The reason I say this is people freak out the most over the assumption that their information can be stolen from the device. If all that the device carries is an identifier, the guest's identity and financial access are relatively safe. Think of it as the barcode on your KTTW card. The computer looks up your guest file in the WDW Intranet and the computer, not your card or RFID bracelet, brings up your identity or charging priviledges. Even if a scammer were to clone it, the worst they could do would be to charge things to you within WDW, and that would be easily trackable as you could sit down with security, review your RFID use log, and security could use the pattern of uses to track down the scammer. Without access to WDW's intranet, the information on the RFID itself would be useless. Also, if the biometric scans remain in place, that would decrease the likelihood that the scammer park-hops with your borrowed identity, and make it easier to catch them if they attempt to do so.
Since that's how the KTTW cards function already, I'm going to assume WDW will handle the RFID system the same. The only added weirdness is that it will make it easier for WDW to track your physical location, but in all reality, the software to do that via surveilance cameras already is cheaper and more readily available than ever before, so I'd be surprised if WDW didn't have some level of that in place already, and other places are already tracking you whether you know it or not. Welcome to reality.