It would be considerably cheaper to buy a "superzoom" bridge camera. Quite a bit smaller to carry around too.
With the cost of high quality 600mm lenses now reaching into the $$$$ range, it would be far less of a loss should you damage/lose or have someone steal your big, attention getting camera bag.
The superzooms have become a popular segment of the camera market due to a few interesting factors. First, as a single lens camera, the camera's sensor/processor and single lens are all tied together from the get go. This provides the designer/manufacturer the knowledge to design one single function device as opposed to the Swiss Army knife systems of an interchangeable DSLR. Since camera and lens profiles are now a part of a modern digital camera, many of the shortfalls of a high powered zoom lens mated to a discrete camera body can then be designed for best overall performance. First, from the lens and secondly, from the camera as a system. This often gives the superzooms an advantage in image sharpness across their considerable focal lengths and their aperture range.
Considering the smaller sensors of the typical superzoom, a longer (relative) reach from the lens results in more image data finding its way to the sensor. Where your 200mm lens placed the subjects in about 10% of the frame, a superzoom with the equivalent to a 1200mm or more lens might have filled, say, 80-90% of the frame. Obviously, the more pixels you can fill with usable subject data, the greater the clarity/detail retrieval of the subject and the more you can further crop in post production without introducing significant noise issues.
Here are a few examples of a superzoom in action;
Favorite Canon SX50 HS Photographs - Tony Britton
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"SX50 beats all my DSLRs"
STOKES BIRDING BLOG: Canon SX 50 HS for Bird Photography: I love this camera!
Obviously, none of these photographers carry only a superzoom. They use the tool when it is the best for the task and have far more expensive cameras and lenses available.
Think of the superzoom as a compact, highly affordable package which can be at your side almost constantly. It's perfect for those shots you come across and there's no time for setting up a DSLR with a super long lens.
One further advantage to the superzoom category is their general ability to operate as "macro" cameras.
Macro lens vs p&s camera for macro shots | Page 2 | Photography Forum
The most likely downside to the superzooms is their low light capabilities - or the "speed" of the lens. Most have modest to good light gathering potential so they are not ideal for fast moving subjects not extremely well lit outdoors and even less so as light levels fall. However, compare their minimum f-stop to that of a moderately priced 600mm lens and you'll see neither lens is ideal for that situation. That takes you into the specialty category of lenses and significantly ups the cost.
The slightly lower mega-pixel rating of most superzooms is offset by the image magnification of the smaller sensor/lens combination. Though, if you want to blow up your shots to a wall sized 20X30" print or larger, then you'll probably want more than a superzoom.
Calculate the costs involved in the DSLR/zoom pairing and the convenience of the superzoom vs the extra baggage of the former and the superzooms are showing more and more why they are a wildlife photographer's go to camera.