It has been argued that, given enough time and money, anything digital can be programmed. But that doesn't mean it's cost-effective to do it in view of the potential marketplace return on that investment. The simple (but to some, uncomfortable) reality is that what ultimately matters with regard to features in New Opera is purely what Opera ASA thinks matters. Opera's viewpoint involves both what it thinks the majority of the marketplace participants want, and the coding/testing costs Opera believes will be necessary to achieve the given array of features it thinks the market demands in order to make the browser worth developing in the first place. As it all unfolds during development, the "reading" of the marketplace and the cost to create a feature can and will both change, not to mention the discoveries made along the way regarding serendipitous ways features can be combined or piggy-backed or the discoveries that certain things can't be done at all in the ways anticipated at the outset.
Opera has already categorically stated that ordinary RSS and integrated Opera Mail will not be returning in New Opera. So I'd accept that as a pretty clear "given", since it shows a strong mindset in that regard.
Opera has also said that a lot of the detail configurability of Old Opera will not be present the same way (if at all) in New Opera, though it's not clear just what that includes, nor whether it's because of difficulty doing certain things in Blink that were easy in Presto or because they believe the demand is simply not big enough to justify the efforts needed - or both. Probably not even Opera fully knows how this will turn out, because this is one area where developmental surprises rule.
Personally, I believe Opera will continue to add various features to what it develops, whether or not they are Presto-cloned - that is its track record for many years. And that is, after all, how any browser flavor distinguishes itself from its competition in the marketplace. So it will always remain something of a work in progress. Each user will have to judge for himself, at any given point in time, how that current version meets his needs or wants, all against a backdrop of alternate browsers (either Old Opera or non-Opera). Currently I'm using Firefox 26 as a primary browser and Opera 12.14 as a secondary one. But I'm keeping abreast of New Opera as it evolves in case it finally achieves some usage elements that I deem necessary; at the same time, I'm continually looking at other browsers as well for the same reason. In the past, the Old Opera versions, with their remarkable capabilities, had largely relieved me of the need to do that, but those days appear to be gone for good, so I'm doing what I need to do.