For those worried about wait list conversions, the trend has been a batches of conversions a week or two after sellouts, likely due to P1 allocating more or their stock to SS. If you put yourself on the waitlist after today, it will probably rely on cancellations, so chances are much slimmer.
As much as I love P1's work, I wouldn't trust that 1:3 comic movie pieces are a good investment just because SS's quarter scale stuff is inferior. The space required to display these almost requires these to be your absolute favorite versions of the characters and P1 is unlikely to slow down their output or not continue to improve their production on later versions, so very few are going to want to pay inflated prices for lesser versions or outdated costumes from whatever comes out next. With this Snyderverse line in particular, we don't even know what the DCEU will look like by time this ships mid-2019. Buy these if you love them, but I wouldn't expect to do much more than break even, unless you plan to flip them while the preorder hype is high (rude.)