For now, the King .com rules.
We can't know the exact future of the new G's, but it is certain that some G's will succeed and others will fail.
But, for now, it doesn't look good for the new G's, and I say this as someone who has invested in a few of them, so what I'm saying is not sour grapes.
Some of the dodgy practices by some registries are mind-boggling, such as the current clawbacks by the .ooo registry. How can one instill customer trust, when the foundation of one's business is built on shifting sands? More than anything, the blatant greed demonstrated by the registries could kill the new G's even before they get off the ground.
Also, even if the registries were filled with pious altar boys, keep in mind that not all forward-thinking inventions have succeeded. Buckminster Fuller's famous "Dymaxion" (... which was not an automobile per se, but rather the '"round-taxying mode" of a vehicle that might one day be designed to fly, land and drive — an "Omni-Medium Transport" for air, land and water -- Wikipedia) was a miserable failure. On the surface, consumers en masse should have fallen all over the car that could morph into a flying car and a watercraft, but they didn't, and we are still stuck with our old boring land-locked vehicles. It is more likely that improvements in the automotive industry will focus on self-driving cars and better roads that are connected to the web and avoid anything that fills an already-crowded and scary airspace.
The bottom line: if the masses don't adopt the new best thing, it will fail.
It is possible that greedy ICANN and its naughty stepchildren have created a need that is, well, not needed. One could live an entire life without a new gTLD and not even notice or care. Heck, I know several people who barely know .com, except as a curiosity...
From a practical standpoint, the new G's are not really "needed" in the sense that mobile phones are needed (which explains their breathtaking popularity in a short time), for a dotcom offers an infinite number of possibilities -- some of them notoriously bad, of course -- but small business owners don't seem to care, judging by the awful urls I see every day on billboards.
So while I would love the new G's to take off in a spectacular manner, I don't think they will, until ICANN and the registries get their sh*t together and begin thinking long-term and less on the quick buck, which means offering a stable and reliable product at decent prices.
Most importantly, Ma and Pa small business owners need to be convinced that MaPaFood.Store is better than MaPaFoodStorePodunk.com, and that task will be up to the registries, not domainers.