Will the market go down further? If so, what do you do with your current portfolio of ETFs, stocks etc? Do we sell or hold?

What market are we talking about here? I don't believe the S&P will correct more than 5% at most. Because look at how strong the bull momentum have been for the past 5 years, it has shrugged off debt ceiling crisis, Ukraine crisis, Tapering and Europe Crisis. Unless some black swan event occurs, I don't see a meaningful correction coming. I feel it is much safer to follow the trend instead of betting on market tops. I do feel like emerging market equities will continue to slide, with USDCNH and copper financed carry unwinding, I see a lot of weakness coming to China in the short term. Also the Russian situation is not certain, the ceasefire ends on the 21st, the Russian markets will also be volatile. Turkey is another thing, the Lira has been weak since the start of the year and protests are not stopping anything soon, so weakness there as well. There might be a flight to safety where emerging market equities and debt are being sold off and piled onto US equity and debt. If you own US equity just old. Read the comments to this answer if you are not convinced. These are just my speculations so if you lose money don't blame me. Remember trend is your friend, just because something has gone up in value, it does not mean it will have to come down anytime soon.

Hold. If the market goes down 10% or more, buy more.