It is never too late to switch to the short side. The issues that drive UVXY ever-downward are the same now even with the low VIX. Have you seen the term structure? How about that daily roll? Are you familiar with levered decay? Look these up and get short Monday morning. Don't even look at your account for 1 month. Then check back in and add to your short (you will have made money but your short position will need increased as UVXY will have dropped 10-50%). Do this once per month for a year and you will at least double (probably more like quadruple) your money between now and the end of the year.
Generally a good point. However, a couple issues. #1 you need capital management. How much are you initially deploying, when are you average up if it goes against you? #2 it is often impossible to get shares to short, at least at Ameritrade. 100% per year seems very ambitious. If you start with say 20% of your capital and then continue to add to the position as it goes down so you have 20% short at all times, figure UVXY drops 25% in an average month, that's 4% per month which is not close to a double. And there's always the chance it can go up 500% like TVIX. I know it seems impossible right now, but it could happen.