Personally, lots of people might feel skeptical for another series in the franchise for a bunch of reasons. A major one is when Nick pulled Korra from on-air and decided to put it on their website. By doing so, lots of fans assumed that Korra wasn’t doing so well. But Korra did somewhat better online, and the reason it didn’t do well on air IMO is because of Nick’s poor advertising and scheduled times. The ads were good but really didn’t grab Nick’s majority of audiences.
But I think it will go on, because you can’t really ignore such a profitable franchise, and I agree with you that it might take a while before Nick allows for another series to continue.korra might just need to feel in more views on Nicktoons or something before they can continue with another series. Plus, no one expected another series after ATLA but here we got Korra. Similarly, I believe that we will get another series, but it might just take some time.
There’s also apparently a petition for Hulu or Netflix to buy LoK/ATLA. There’s a forum post on it if you want to check it out.
I get that you might not be able to read the comics but you should definitely check them out. It might sound weird but there might be YouTube videos of the comic pages shown, so that you can read them on there. It’s not as good as getting the comic itself, but hey, at least you’ll be updated. And even with the comics, it would take forever to get all the possible story lines finished, which is why I think another series should be coming out. I mean the best we can do is hope, and help promote Korra as much as possible.