The next game i'll be making, which I am going to devote most of the next year to, is going to be a multi-player game from the ground up, so I will make use of TNet extensively in the process. Since using the tool is the best way to find way to improve it, you can expect good things to come to TNet.
If by server migration you mean clients automatically choosing a new server if the existing one drops, then yes it's a planned feature.