The Skyliners will be up and running prior to Star Wars: Galaxy's Edge opening at Hollywood Studios. So, short of a major natural disaster, you can count on the Skyliners being accessible for Christmas, 2019.
Pop vs. CBR? There's no way to predict the weather, but CBR wins the pool competition, easily. Plus the CBR has spa whirlpools which are most definitely heated; Pop doesn't have those. If the weather's nice and you have small kids, the Aquaplay area at CBR is outstanding, and beats the fountain fun area at Pop.
Dining? CBR wins. There will be both a food court and a sit down dining area (the re-opened Shutters). Plus, Spyglass Grill is pretty sweet quick service restaurant; it is open to the elements, however.
Buses? Pop wins. Pop has one of the best bus services in WDW, plus with a bit of extra walking, you can also use Art of Animation's bus service.
Resort size? Both resorts sprawl, and while Pop isn't as spread out as CBR, CBR has an internal bus service.
Theming? It's about personal choice, but CBR wins, easily, for me. The place is lush, and really has a nice "Island Life" vibe going, and always has. Pop's theming is fun, but it's overwrought, and I can never get nostalgic for hippies, having had the misfortune of smelling them in my youth.
Rooms. Here's where it gets interesting. The last time I stayed at Pop was 2014. We enjoyed it, but we missed the roominess of the CBR. We're just back from the CBR, which has had a room refurbishment, just like Pop. Everything I've seen about Pop's rooms says that Disney has done an outstanding job in maximizing the utility of the 260 square feet of a Pop room. With the Murphy bed up, you get a decent chunk of useable space back, and both rooms have coffee makers, mini-fridges and make-up mirrors. Only one sink at Pop vs. two at CBR, but 2 showerheads at Pop vs. 1 at CBR. I give a narrow edge to the CBR. At the end of the day, Pop still has 260 sq. feet to play with, while the CBR has either 314 sq. feet, the standard moderate size at WDW, or 340 sq. feet, as a number of sources continue to insist, due to it having been the first non-deluxe resort at WDW.
And the CBR room refurbishment has produced a darn nice result. We stayed at the Beach Club for the first night before moving to the CBR, and point for point, the room at the CBR held up very well compared to the Beach Club (yes, Beach Club wins, but it was a lot closer than I expected).
All things being the same, I'd still stay at the CBR over Pop. Pop is nice, but at the end of the day, even with a fold-up bed you get more elbow-room than at Pop. Plus the pool is better, you're on the main Skyliner hub and you have more dining options. The only clear advantage for Pop is the bus service, and we don't know how, if anything, this will change after the Skyliner goes online.
Last piece of advice: Go on YouTube and search for room tours. People are constantly putting them up, so you shouldn't have problems finding current room tours.