I think everyone can guess my long term sentiment towards Monero:)
Short term I don't recommend anyone use margin to speculate in either direction. There is a lot of BTC moving around right now, partially because of Ethereum. Volatility may remain high and Poloniex still does not disclose the amount of open margin loans
Leverage is interesting thing as people take loan upon loans. Potentially this can create a bubble for Monero. However, it might be pretty ugly when the bubble bursts. I certainly hope there will be some shorts also to be filled when this happens just for the sake of markets. Reminds me from US housing bubble in 2000-2007.