Nowhere on Tracfone's website is any mention of the Motorola c257 or v176, but now there's a sleeker, more modren, closer equivalent and successor to the c155: the c139. The main benefits are that the c139 looks better, is a little smaller (though not by much), has a better screen (16 bit vs. 12 bit, one extra pixel tall) and has a good bit better battery life, clocking in with at least 8 hours of talk time and 16 days of standby time, with phonescoop's information saying it's even better (11.67 hours \ 18.8 days talk\standby times), versus 6.67 hours \ 12.5 days for the c155. Oh, and the phone can store 100 contacts on the phone itself, whereas the c155 has no internal memory for this purpose (everything's on the SIM) and has precious little memory otherwise (300k). Granted, I still hope that Tracfone will come out with the c257 (I don't really care for the v176 as it's pretty big but it'd be nice too) but this model is more in line with what they have already and if they price it like they are pricing the phone it's succeeding ($30) I'll bite, if only for the bttery life and the cheapness.
Here are some links to info about the phone:
Motorola (preview page)