Hrrm unfortunately there doesn't seem to be one in the future. My lumia 1020 still works beautifully though even with the latest windows 10 os update but as time goes on so does technology and eventually even a small sensor will surpass it in image quality.
How does the 950 compare? People seem to be gloating about the camera, some saying its better than the 1020?
I would say the Pansonic CM1 is the spiritual successor, it probably edges out the 1020 in image quality thanks to it's lens and newer backlit sensor.
After the Panasonic I would say the 23mp Sony Xperia Z5 would be next in line. Sony has been stuffing the same sensor that they use in their cybershot cameras in the xperia z series since about the z3 was released and the results have been pretty impressive despite the sensor being a bit smaller than the 1020's(but still bigger than the usual cellphone sensor as it's a full fledged digital camera unit) I'm willing to bet this phone would actually give the 1020 a good run.
Not sure I would recommend the LG G4 for image quality, I really don't feel it offers anything special imo. Focusing seems to be it's strongpoint but otherwise it's image quality is the same as the galaxy, Motorola etc. .It really isn't in the upper echelon of camera phones imo.
I'm vey apprehensive when it comes to android though. It has never felt polished and over time the user experience degrades, they're known for getting laggy and slowing down to a crawl with age. The only real solution is to do a clean factory reset and be very leery of which apps you download, have a memory cleaner app handy etc. . .I'd say IOS carries the polish and tight integration that you'll be familiar with and you'll be able to use it for years without any issues and they won't have any issues with certain apps acting weird because ios isn't fragmented like android. YMMV and if you're the type to get a new top-end phone every year then it may not matter.