i don't hold any of them in first place to want to decide what to do when they get dumped! we all know that sooner or later all the altcoins out there are going to get dumped so the only question is when to get in and how long to stay in.
the answer depends on the market itself and the potential of the ongoing pumps that the specific token has. then as soon as that pump ended you must make your exit instead of waiting around.
you are very wrong when you said that all the altcoin will get dumped sooner or later. To be honest with you, most of them will never get dumped. By your statement, you are implying that there will come a time when we will have only btc because aside Bitcoin any other token or Coin are altcoin