I still have this from it showing up free on PS PLus a couple of months back. Am I gonna be lost if I jump right into this one without playing the first?

I played it from the PS+, never played anything else related. I didn't feel like I missed anything story-wise, and I really enjoyed the game.

You won't be "lost," but Last Light is a direct sequel to 2033. Same characters, continuation of the same story. And although Last Light is a very good game, 2033 is even better and playing the sequel first will spoil a lot of the original story along with the ending.

I wonder if this will sell really well, due to the fact that there's so many PS4s&X1s out there and so few games for them.

Probably not. Both the PS4 and XO have had only a dozen games or so that have sold over 500K units worldwide at a retail level.

While there are over 15M+ next-gen consoles in homes, suffice to say, most people who own them aren't ones to be consistently buying new video games other than specific, AAA event titles.