Doubt it. Opera never had more than fumes of the browser market and power users such as myself make up a very small percentage of total browser users, so it would seem this new browser targets the minority within the minority so to speak. I've used Opera and usually had it installed for web development testing even though I never used it much for my own purposes, I did go through all of its features etc. and it was an ok browser overall. It just didn't have enough differentiation of things that matter to sway enough people toward it I guess.
When it comes to browsers for power users, the 800 pound gorilla in the room is Firefox. Out of the box without addons Firefox has consistently had more features and functionality exposed to the user via the user interface, pulldown menus, and configuration dialogs than any of the other major browsers as far back as I can remember. Every browser has individual features that the others don't which can be used to promote them in some way as superior, but taken as a whole, I believe Firefox stands out as the Swiss Army Chainsaw of browsers.
Then we get to customization, and Firefox has always had endless numbers of addons available for it for just about any purpose, some of them high quality and some of them crap, but overall the sea of addons is virtually endless, and even more so when looking at Greasemonkey and similar addons which themselves have addons.
Now I'm not in any way claiming Firefox is the absolute superior browser hands down for all people for all purposes, as I don't believe that is true for any browser now or ever in the future. I think it is a very individual thing because everyone has unique needs and preferences or we wouldn't have multiple browsers to begin with. But in terms of the number of power features available out of the box, and via addons I believe Firefox will always be the more widely used browser of power users, and another reason for that is existing market share. Even in 2015 websites out there have to be customized and tested on every browser in order to ensure compatibility smoothly, and for sites that put that much effort into their design they will most likely test their site on Google Chrome, Firefox, and IE, as well as the most popular mobile browsers before considering browsers that are catered to ever diminishing numbers of users such as Opera or the various open source browsers etc. It's just a numbers game for web developers.
One thing Opera or any spinoffs of it has going for it is sharing the Chrome engine, that makes rendering compatibility issues less of an issue potentially, but the problem it faces is that power users in particular tend to find power tools and stick to them like glue. We generally don't like to hop from one application to another as we build up years of comfort using one tool and muscle memory etc. Replacing your software with other software is painful, even if the other software is twice as good.
Hard to know in advance how any new browser will fare in the market for any target user, but I think it's a hard market to break into for any new product no matter who the target user is intended to be. They all end up having to contend with the existing momentum of the giants. It's not impossible, but it isn't something that we see happen very often either. Google Chrome's rise from small to big is the last example I can think of in the browser market of this happening, and that's backed by the full financial might of the mighty Google.
I'll certainly try out Vivaldi with an open mind and if it is useful I might end up using it alongside my other umpteen browsers, but I'd fall off my chair if anyone could ever put a browser out that would make me want to ditch Firefox as my primary browser. I'm not opposed to it, just highly skeptical I'll ever see it happen. :)