I hate to break it to everyone but the Solo is already an old dog; good ole dog, but old. There are so many good things about Solo, but so many weaknesses. The platform is good, motors and esc's are strong, frame is also sturdy. Batteries will dry up, or someone will make them. However, at this time batteries (like gimbals were) ARE cheap and apparently plentiful. They are at an all time low; less than $45 Ebay. Considering that my racer Lipo is 14.4v 2200Mah and are $35 Solo batts are a great deal. Parts are also readily available. So that part of the Solo question is good.
However, to get any real performance in distance you must install an upgrade RxTx card and antenna ($$$ and some time and know how in changing cards). Even then I haven't found the range to be worth a shit. So that is a weakness. Then there is the sometimes erratic nature of Solo to do things that are %^cked up. Like trying to take off after a rough BUT landable touchdown. What a POS! And some are reporting fly offs.
Second: and IMO the worst part about Solo is the lack of ANY extra channels/switches. That is lame. And although there is a nice group of people here, there is virtually no one (some butttttt rare-I can't find em) that are doing exotic mods on Solo: OSD, Sonar, Optical flow, multiple cameras, FLIR, full telemetry, stereo optic for 3d, or a myriad of other things that I have in my own builds (I have built ALL of those mods in, and have found many posts by hobbyists that will help set up a custom ship.) So that leaves the Solo as a just a platform to take pictures. (errr well only up to Hero 4, Hero 5 no fit sorry bout dat) So Solo pics will only be to Hero 4 specs. New and better camera specs leaves Solo farther back even more. But if one can be happy with the design and function Solo does then why buy another/newer/spendy'er?
That leaves the gimbal. Once the gimbal does not operate the Solo becomes a dinosaur; that fast! Once the gimbals dry up they WILL escalate in price. But only to the point of how cheap the Solo is at that time. At this writing I bought a guaranteed used one on Ebay for $137 wIth shipping. That's about the same average price for a good gimbal of anyones. So it's not crazy yet. And if you're comparing: A Mavic repacemnet gimbal (with camera; only way to buy) is $275 Ouch.
So far Solo gimbals are cheap; just like Solo.Treat them right and Solo will continue to give a complete camera platform. But if you are going to stay in this hobby Solo will be replaced. There are just too many great quads for the future.