Take my opinion with a pinch of salt as I've only been around for a few months.

If it's like last time, alts in general will drop by a greater degree than BTC, LTC will be stable and may rise if people jump on it to avoid the dip (LTC rose last time BTC fell, and didn't rise when BTC rose, it stayed roughly in line with fiat, seems to be more disconnected to BTC than most). A few alts will buck the trend and go up or remain steady, and may gain steam if people think they can use it to avoid the dip.