Lightning is something that will later on affect the market positively, because that presents an opportunity for people to 'stake' their coins by locking them up in Lightning channels to scoop up fees. It wouldn't really surpise me if there are like 50,000BTC locked up in the Lightning Network within 5 years. The more coins are locked up the less that can be sold on the market, it's that simple.
yup, it's impossible to predict but exciting to speculate about. metcalfe's law/network effect should apply to lightning the same way it applies to bitcoin. if it ever experiences the same kind of exponential adoption, we're talking about an insane amount of supply being locked up in LN channels. that could have a huge effect on price.