As I myself "upgraded" from a mega-zoom like the SX50 - in my case the Sony HX100V - to an A3000 back in 2013, perhaps I can offer some thoughts. I did a quick check of SX50 specs in order to compare it to the experience I had with the HX100V and then A3000.
The SX50, like the HX100V, being a lower-cost mega-zoom bridge camera, is equipped with a 200K dot viewfinder, about the same as that on the A3000, so your brother is not likely to feel let down by the viewfinder. Many here, used to the higher density EVFs of the NEX-7, -6, and A6000, not to mention the A7-series, rightly view such a viewfinder as inferior. But if you've never used better, you may not miss the better resolution.
The SX50 apparently has a 460K dot LCD monitor that tilts (Canon's "vari-angle"). My Sony HX100V also had a tilting higher-resolution (920K dot) LCD panel, which was noticeably better than the fixed 230K dot one on the back of the A3000. Indeed, this was perhaps the greatest weakness of the A3000. Your brother may find the LCD to be a step backward. However, I'm not sure the difference b/w 460K and 230K will be as noticeable as that b/w 230K and 920K. The lack of tilt may be limiting in strong daylight outdoors though. That was about the only time I would revert to using the low-res EVF on the A3000 rather than the LCD. If bright light shooting with a tilting LCD is critical, that would be one notable consideration.
In terms of just about everything else, except for autofocus speed and continuous shooting frame-rate, the A3000 was a major improvement on the megazoom HX100V in my experience. And the larger body and grip (versus the other NEX and Axxxx models) made it easy to switch from the similar-sized and shaped HX100V. The image quality from the A3000's APS-C 20.1MP sensor was a huge improvement on that from the HX100V's (and presumably also the SX50's) 1/2.3" 16MP sensor. In fact, I still don't see much improvement IQ wise from my newer A6000 over the A3000. In terms of functionality, the A6000 surely beats the A3000, but for a "starter" large-sensor interchangeable lens camera, the A3000 is, in my humble opinion, a great bargain. Especially since A3000 bodies can now be easily had for under US$200....
See
SONY A3000 DIGITAL CAMERA BODY {20.1 M/P} - KEH Camera
That's my two-cents worth. I hope it helps.