Well, as to your last point, UVXY would have to spike to above 40, to OTM on the (UVXY1) LEAP expiring in January. Not likely, I think.
Looking back at what I wrote, I don't think I expressed myself very well: the issue isn't so much the option expiring worthless as it is the option expiring worth less than what you paid for it! (You can cross out "leave the options worthless" and replace it with "leave your net position underwater" in the second to last paragraph.)
These are very expensive options (specifically because the VIX term structure is often in contango, UVXY often erodes quickly in value and so they cost a lot.) Because the options are expensive, they have to expire heavily ITM for purchasers to be profitable. You're paying a lot of time premium.
I don't know when you bought or how much you paid, but today the mid on the UVXY1_4_P was about $2.75. So, to break even, someone who bought today will need UVXY1 to close below $1.25 in Jan. ($4 - 2.75 = 1.25) That's equivalent to $12.50 on UVXY and today UVXY is trading in that ballpark. So, you'll break even if UVXY is at around the same price in January as it is today. You'll lose if UVXY goes up... virtually at all. Granted you won't lose the entire amount unless UVXY spikes to 40, as you correctly point out.
Note that UVXY is (slightly) higher than it was at the beginning of this calendar year. For nine months it has been between about $9 and $22. It wouldn't take much of a spike to make this a losing trade.
Also note that the VIX futures are NOT in contango right now, so you don't have that force to erode the price of UVXY at the moment. If every VIX future's price froze in place for the next 3 months, UVXY would still rise. You need VIX futures to drop and/or the VIX term structure to return to contango and stay there for a while, ideally both.
I'm not saying your call is wrong, just that there are lots of things to look at here. This is not a "normal" option on a "normal" contract... and so its pricing is unusual. It's not "too good to be true," but neither is it quite as it seems, perhaps.