The price of altcoins is falling down on the wave of coming fork, so it is the best time to invest in altcoins, but I suppose prices will fall a little bit more during those last days before the fork. I plan to buy Etherum and Litecoin, yes, they both are not so cheap, but this coins one of those who will have a future with 100% guarantee.
I think it's better to stay in fiat because if Bitcoin price falls altcoins are also likely to fall.
Ethereum and Litecoin are good altcoins for long term investment but you can find cheaper price for them next few months.