I'd wait for someone to post a review first honestly. Looking at those older 2080 Ti's on gigabytes page I've noticed two things that might effect cooling.
1. It looks like their old 2080 Ti Turbo used a copper plate to an aluminum fin array? That would definitely negatively effect cooling. It looks like their plans for a 3090 Turbo use a full copper heatsink.
2. It looks like the design of the 2080 Ti Turbo also had a plastic shroud, but this time they're going with a metal frame to help dissipate heat. I'll wait to see how it performs of course.
I honestly will probably stick with my 2080 (even though it's now very out dated before I've even had a chance to really use it) simply because I have it. Though driving 5,120 x 1,440 might be difficult for it. While blower style GPU's are always significantly louder, it's important to remember how small the Mjolnir is. Even with a sandwich lay out, the possibility of heat soak or heat bleed-over between the chambers is very possible. A blower style GPU may help prevent that.
The 20x0 line is still my favorite looking card at the moment, so I'm not entirely disappointed in being a little bit slower. It'll also be easier on my system's PSU. As I said, I think I can marginally get away with a 3090. If I keep all my clocks stock and/or considering undervolting a bit. But a 3080 would likely be fine.
