Nikon has announced the AF-S DX 18–140mm f/3.5-5.6G ED VR lens, and despite the pent-up demand for anything new on the advanced enthusiast front, it's probably not what the advanced shooter crowd is looking for. To get one thing out of the way, this (probably) isn't the kit lens for the hypothetical D400. The fact that it's being announced with the new SB-300, ostensibly a replacement for the SB-400 flash unit ought to tell you something. Also, the Coolpix L620 is being announced on the same day; even though Nikon can be haphazard with their marketing at times, this isn't the case. It's solidly a consumer-oriented announcement day. Having said that, I wouldn't be surprised if it was bundled in a D400 kit, but the fact remains, the more serious photographers out there will be looking for the body-only form.
The new 18-140mm lens replaces the long serving Nikkor f/3.5-5.6G ED VR AF-S DX lens that was the kit lens on theD90, D7000 and D7100. In fact, it's pretty much a modern version of the 18-135mm f/3.5-5.6 G IF-ED DX kit lens that came packaged with the D80. That was an unusually sharp lens for the it's price range, but it suffered from high degrees of distortion, vignetting and lateral chromatic aberration. In many ways, the 18-105VR was a tamed version of the 18-135; by backing off on the focal length, a slightly better compromise could be made optically. In an oblique way, the 18-140 will also supplant the venerable 18-200mm; due to focus-breathing, the actual object magnification wasn't that much greater than the 18-135mm when focused at objects at close range.
However, the 18-135mm was never marketed as the kit lens for the D200; during that era, retailers would have generally sold it with the AF-S 18-70mm f/3.5-4.5G ED DX lens instead, which dated to the earlier D70 launch. The aperture range of the 18-70mm was acceptable for D200 shooters, but a variable aperture lens that is f/5.6 at the long end was and still is unsuitable for the advanced shooter crowd. Also, it's a long standing rule of thumb, but one that still stands true; a quality zoom lens should approximately have no more than a 3:1 ratio of its longest and widest focal lengths. The 18-140 obviously exceeds this, but this type of lens is about balancing convenience against value and performance. If this lens is bundled with the D400, it'll be more of an unwelcome nuisance than anything else; sure an optically competent lens of this range would be nice to have, but it's not a lens that semi-pros would add to an existing collection given the choice.
The layout of the control rings is familiar if you've used the previous kit lens. The zoom ring is wide and fat, as the majority of the users of this lens will only rarely use the AF-override feature. The focus ring looks to be similar to the 18-105VR; I can only hope that the tactile feel has improved, because that was one of the reasons that actively discouraged you from using the focus ring on that lens. However, most of the new generation of Nikon lenses have shown tangible improvements in image quality over the previous eras, and the 18-140 shouldn't be any different. In fact, good news! It comes with a proper metal lens mount!
As for the reason why this lens exists.... it's because of the internet. Anybody buying the D7000 or D7100 now will be reasonably well-read and knowledgeable about equipment. A high percentage of people who are shopping for these cameras will pass over the 18-105VR for a more capable lens, possible with one of the third party brands. However, Nikon can't sustain a business of selling only camera bodies; it needs the lenses to keep cash flow up. That's why early shipments of the D90 an D7000 came in kits only; Nikon made sure that early adopters bought a lens along with their new cameras... whether they needed it or not. The problem is that successive iterations of this strategy has flooded the user base with kit lenses... if you are trying to sell a 18-55VR on the used market, good luck. Also note that the retail price of this lens has moved up from the 18-105. This is what's known in marketing as "preserving average selling price." Initially, both the 18-105 and 18-140 will coexist in the lineup, but I can see a day when the 18-105 gets phased out. A D7xxx camera with the 18-140 would be able to continue to sell in bundled form for a launch price of $1,400 or more; because of the passing of time, the 18-105mm will fall further behind camera performance. It's adequate for 24mp today, but in two-three years time, it would be a stretch if Nikon's APS-C cameras move to... oh, say 36mp.
18-140mm is roughly the equivalent of the old 28-200mm superzooms from the film days. If you aren't ambitious about expanding your lens collection, this is about 90% of what most family shooters really need. However, like the 18-105VR, you will probably eventually pair it with the inexpensive 35mm f/1.8G AF-S DX to play with depth of field control and to make up for lower light conditions.
This lens isn't about the semi-pro crowd, but about shoring up revenues in the fattest part of Nikon's unit volume; the D5200 to D7100 range. That's not exciting for the enthusiast crowd, but it is incrementally better in how Nikon markets to the middle market; it takes away those "I'm looking at the 18-105mm lens, but I heard it's not good enough for the D7100..." questions that get in the way of purchasing decisions. As the old saw goes, you have to remove the frictions and impediments that make buying more complicated for your customers. A boring launch; doesn't really move the camera business forward for Nikon, but in the years to come it will help prevent the erosion of the mass-market-middle in a time when mirrorless cameras are threatening the DSLR market from the bottom.
Update (October 2013): As predicted, you need to watch out for the price bump that this lens causes if you are shopping for a kit lens. The recently launched D5300 is only available with the 18-55mm or the 18-140mm; no 18-105mm. The list price is $1399 USD, which is almost the same as the D7000 kit when launched, and to be honest, quite expensive for a mid-range consumer DSLR. The difference in list price between the kit D5200 with the 18-140mm and the 18-105mm currently is $300 USD. Watch out for availability if you are budget conscious, it's in the interest of retailers to stock the more expensive lens and to limit supplies of the older one.