That's a fallacy. PoS holders are also looking to sell for a profit when they decide to get out.
With miners at least there's a floor price because miners tend not to sell coins cheaper than the cost of mining them. Though that's not always the case.
But with PoS there's no floor, the price is completely arbitrary.
Besides, why would you want to hold a coin for months for a few percentages when the price changes drastically even on a daily basis?
And since it's completely free to stake coins (you just have to own them) everyone staking will earn at the same rate so everyone will just have a few more coins but you still need buyers to increase the price of a single coin.

Also, the multi algo PoW what makes this coin unique in the first place and PoS would take that away turning this coin into just another generic coin. At least go for PoW+PoS to keep that.

I know PoW has plenty of issues but I really don't get how people can take PoS in crypto even remotely seriously, it's pretty much just gambling. /rant