Without actually seeing it or hearing it for my own eyes and ears, I can't (and won't) say a definate yes or no if it's shot or not. However, I'll give you some things to think about and look at, and leave that for you to decide.
Does it burn oil? Any leaks? Any other check engine codes? Any pinging, rattling, or so on? Overheating?
For sake of argument, let's say that this cylinder misfire and the compression are the only problems this engine has. It's on it's way out for sure, but it could be a while before it actually bites the dust and leaves you stranded. That being said, I would not trust the drivetrain to take you any further than a grocery store. Towing, offroading, long trips etc should definitely be avoided.
Once the engine eventually dies, you're left with a couple of options. You could part the truck out or sell it as is at that point for someone to make a project out of, while at the same time getting some dollars towards a new vehicle. Or, you could put a different engine in if you're so equipped, or if you have the funds to pay a mechanic to do this.
If you choose a new engine, that's a prime opportunity to upgrade. For example, it's worth while to kick the 3.slow to the curb and upgrade to the 4.0 SOHC, esspecially if the transmission is shot, too. However, changing over to a different drivetrain all together is a lot more involved than putting in another 3.0. New computer, harnesses, transmission, of course the engine, etc will be required for a different setup.
Something else to keep in mind though is the rest of the truck. If your Ranger is rotting out or has a lot more problems, it may not be worth your time and money to fix it.
So, take a good look around the rest of the truck. Undercarriage, panels, paint, interior, etc. Evaluate the truck and go from there. There's plenty of options to choose from.
(But yes, I do think your engine is shot)