I would NOT switch to altcoins now. The major bull run already happened and bitcoin went sideways.
BTC will move again (either up or down.. does not matter) and this will hurt the alts.

I would leave the portfolio diversified with 60-70% BTC and maaaybe cash out a little before new years. The thing is: nobody can predict the market but look at the sheer numbers. Does it look like healthy growth  to you?