Sony will keep the 3G model around for at least a year. If things haven't improved I wouldn't be surprised if Sony drops it then.
I think retailers in Japan are acting a little too hastily. Tales of Innocence is coming up for the Vita, things will improve with that title.
If I was making the decisions for Sony I would bundle Tales of Innocence with both models of the Vita, but do not raise the prices. A nice limited run bundle. After that I would put either Hot Shots Golf or Wipeout 2048 in the package.