In the current situation, it is impossible to say how far this downtrend will continue, that's why it is impossible to keep all investment at one price, we need to divide the money into parts which will help us to buy the coin when it drops again.
The likeliness of altcoins dropping more is less because it's already dipping, therefore, if there's a an altcoins run, price would probably pump more than BTC has achieved this year. Buying altcoin at this time is a good strategy, that if you are willing to wait for maybe a longer period before it will recover.
Actually there's a lot of altcoins that looks like dead even in the past, but when the market starts to be bullish, they recover and not only recover, they even make a new ATH which I think will likely happen in the future.