Sprint is indeed going to eventually phase out Nextel. It will still hang on for a couple of years just because a lot of businesses use it.

My own experience with Nextel is that those are the LAST phones that you would want to have in the wilderness. Some models might survive harsh conditions, and they will work great once you get into the city, but reception is a problem. Nextel even has absolutely no coverage on I-70 between Denver and Kansas.