? 
For the D5200, Nikon took the body of the D5100 but significantly updated the inside. That includes a new, higher-resolution CMOS sensor, and the same new autofocus and metering systems that debuted in the D600. Though it's been announced in Europe and is slated to ship there in December, the official word from Nikon US is, "Nikon Corporation announced a new product in select markets worldwide but not in the U.S. at this time." However, the D5100 is over a year old, so I can't imagine that the U.S. announcement for the camera is very far behind. Note that the D7000, an all-around excellent camera, remains widely available for less than $1,000, which may affect the company's pricing and release decisions.
The only notable problem with the D5100 in my view is the performance; the D5200 incorporates a newer version of the Expeed processing engine plus updated autofocus, so I'm hoping that the speed gets a needed boost from that. It also has improved video specs -- not so much in its the ability to do a meh 1080/60i as the desirable 720/60p -- plus a built-in stereo mic. While it adds Nikon's full-time AF for video, it's not as fast or quiet as Canon's STM contrast-AF implementation; on the other hand, it doesn't require a whole new set of expensive lenses.
Here's how it compares to some of its competitors, assuming that it's priced about the same as the D5100:
| Canon EOS Rebel T4i | Nikon D5100 | Nikon D5200 | Pentax K-30 |
Sony Alpha SLT-A65V | |
|---|---|---|---|---|---|
| Sensor effective resolution | 18MP hybrid CMOS | 16.2MP CMOS | 24.1MP CMOS | 16.3MP CMOS | 24.3MP Exmor HD CMOS |
| 22.3mm x 14.9mm | 23.6mm x 15.6mm | 23.5mm x 15.6mm | 23.7mm x 15.7mm | 23.5mm x 15.6mm | |
| Focal-length multiplier | 1.6x | 1.5x | 1.5x | 1.5x | 1.5x |
| Sensitivity range | ISO 100 - ISO 12800/ 25600 (exp) | ISO 100 - ISO 6400/ 25600 (exp) | ISO 100 - ISO 6400/ 25600 (exp) | ISO 100 - ISO 12800/ 25600 (exp) | ISO 100 - ISO 16000 |
| Burst shooting | 5fps 6 raw/22 JPEG |
4 fps n/a raw/100 JPEG |
5fps n/a |
6fps 8 raw/30 JPEG |
8fps (10fps with fixed exposure) 13 raw/17 JPEG |
| Viewfinder (mag/ effective mag) | 95% coverage 0.85x/ 0.53x |
Optical 95% coverage 0.78x/ 0.63x |
Optical 95% coverage 0.78x/ 0.63x |
Optical 100% coverage 0.92x/ 0.61x |
Electronic OLED 0.5 inch/ 2.36 million dots 100% coverage 1.09x/ 0.73x |
| Autofocus | 9-pt AF all cross-type; center cross to f2.8 | 11-pt AF center cross-type to f5.6 (Multi-CAM 1000) |
39-pt AF 9 cross-type (Multi-CAM 4800DX) |
11-pt AF 9 cross-type (SAFOX IX+) |
15-pt phase-detection 3 cross-type |
| AF sensitivity | -0.5 to 18 EV | -1 to 19 EV | -1 to 19 EV | -1 to 18 EV | -1 to 18 EV |
| Shutter speed | 1/4,000 to 30 secs; bulb; 1/200 x-sync | 1/4,000 to 30 secs; bulb; 1/200 sec x-sync | 1/4,000 to 30 secs; bulb; 1/200 sec x-sync | 1/6,000 to 30 secs; bulb; 1/180 sec x-sync | 1/4,000 to 30 secs; bulb; 1/160 x-sync |
| Metering | 63-zone iFCL | 420-pixel 3D color matrix metering II | 2016-pixel 3D color matrix metering II | 77-segment | 1,200-zone |
| Metering sensitivity | 1 to 20 EV | 0 to 20 EV | 0 to 20 EV | 0 to 22 EV | -2 to 17 EV |
| Video | H.264 QuickTime MOV 1080/30p/ 25p/24p; 720/60p/ 50p | 1080/30p/ 24p; 720/30p/ 25p/24p H.264 QuickTime MOV | 1080/60i/50i/ 30p/25p/24p; 720/60p/50p/ H.264 QuickTime MOV | H.264 QuickTime MOV 1080/24p/ 25p/30p; 720/ 50p/60p | AVCHD 1080/60p @ 28, 24Mbps, 1080/24p @ 24, 17Mbps, 1080/60i @ 17Mbps |
| Audio | Stereo; mic input | Mono; mic input | Stereo; mic input | Mono | Stereo; mic input |
| Manual aperture and shutter in video | Yes | Yes | n/a | n/a | Yes |
| Maximum best-quality recording time | 4GB/12 min | 20 min | n/a | 4GB/25 minutes | 2GB/29 min |
| IS | Optical | Optical | Optical | Sensor shift | Sensor shift |
| LCD size | 3 inches articulated, touch screen 1.04 MP |
3 inches articulated 921K dots |
3 inches articulated 921K dots |
3 inches fixed 921K dots |
3 inches articulated 921K dots |
| Memory slots | 1 x SDXC | 1 x SDXC | 1 x SDXC | 1 x SDXC | 1 x SDXC |
| Wireless flash | Yes | Yes | No | Yes | Yes |
| Battery life (CIPA rating) | 440 shots | 660 shots | n/a | 480 (lithium ion); 1600 (lithium) | 510 shots |
| Size (WHD, inches) | 5.2 x 3.9 x 3.1 | 5.0 x 3.8 x 3.1 | 5.1 x 3.9 x 3.1 | 5.1 x 3.8 x 2.8 | 5.3 x 3.9 x 3.3 |
| Body operating weight (ounces) | 20.8 | 19.6 | 19.6 (est) | 22.9 (est) | 22 (est) |
| Mfr. price | $849 (body only) | $799.95 (body only) | n/a | $849.95 (body only) | $899.99 (body only) |
| $949 (with 18-55mm lens) | $899.95 (with 18-55mm VR lens) | n/a | $899.95 (with 18-55mm lens) | $999.99 (with 18-55mm lens) | |
| $1,149 (with 18-135mm STM lens) | n/a | n/a | n/a | n/a | |
| Release date | June 2012 | April 2011 | n/a | July 2012 | October 2011 |
While it sounds like a potentially nice camera, the D5200 doesn't really stand out from the specialized competition: Canon has its video-optimized AF system, Pentax has its weather-resistant bodies, and Sony has its speedy models with built-in geotagging. The D5200 supports wireless, but only through the Wireless Mobile Adapter WU-1a USB dongle. Still, based on the popularity of the D5100, I suspect if Nikon decides to ship the D5200 here it would sell enough to justify its existence.