The 55i features a decent size LCD display with a small 6 button paper template at the top.
The 57i has a large LCD for desi-less operation. There is an optional 20 button side-car for the phone (up to 3 can be used) which has the same large LCD on it. Additionally there will be a 57i CT with a cordless handset (a la 480i CT). The handset looks identical to the handset that comes with the 480i CT.
The 480i and 480i CT are expected to be kept on and possibly renamed. Pricing is not available at the moment.