It depends on what you're expecting to happen next.
If oil goes back up then holding an oil ETF, or the shares of an oil producing company, is one way to profit.
If oil falls further or remains at current prices for an extended period then that's good for the profits of those who have oil as a major business cost. Airlines are the obvious example there.
Either way there's an element of risk. Oil is subject to the normal supply and demand forces that affect any commodity but is also subject to political actions. For example, the USA holds a fairly large stockpile (the Strategic Petroleum Reserve) of oil and could flood the market in the short term, thus crashing the price, if they wanted to. On the other hand, that reserve isn't full so they could buy more and so could other countries thus adding "artificial" demand and pushing the price up.
Then there's the major producers who could, either for self interest (higher prices) or political reasons choose to slash production and create a shortage. That has certainly been done before, most spectacularly in the 1970's. Also worth noting that a lot of oil comes from countries not overly keen on the West such that a decision to withhold production may be motivated by factors other than pure economics.
And finally, a longer term complicating factor is that nobody really knows for sure how much oil can be produced and at what price. Eg at $50 per barrel, what level of ongoing exploration, drilling and production is actually profitable? It would be a smaller amount at $50 than at $100 certainly, but whether or not it's profitable to produce at a rate which meets demand at $50 is a big unknown. Many will argue that the current price is unsustainably low, others disagree.
Personally, I don't see the price remaining at present levels unless the global economy falls in a heap and consumption falls or at least stabilises. But even if I'm right, markets can move in the opposite direction to fundamentals for quite some time (potentially years) before the inevitable happens.
I'm not saying don't do it, just be aware that there is no certainty about the future. The only thing that is certain is that oil right now is cheaper than it was in the recent past. But that doesn't mean it will fall further or that it will double in price, the future is inherently uncertain especially where a highly political and relatively hard to store (since it's a liquid versus say, coal, which can easily be just piled up on the ground in the open if someone wants to store lots of it) commodity such as oil is concerned.
But if you were planning to buy a motor home and drive right around Australia, well it's a certainty that fuel costs less now than it has for the past few years.