What are the chances of the original anime being made more readily available at some point soon? It's a perfect time to do it with the new one coming out.
Since the new one is right around the corner, I'd say it's too late for a DVD or BluRay release in North America. We'd have heard something by now if it was intended to be part of the party.
I'd say that maybe the classic series could quietly drop on Netflix or some other streaming website while the new episodes air, but even that couldn't easily be done in English. They'd have to contact ADV (dead) and Pioneer (dead) to put up the subbed version, or contact DiC and Cloverway to get the dubbed version. And even then, season 5 would be MIA, because it was never translated (allegedly due to Naoko Takeuchi blocking it).
Funimation has basically said that they'd snap up the rights to Sailormoon and retranslate it as soon as it became available, they'd even be inclined to re-dub the series because it's as good as gold to them, but every time they asked, Toei apparently said that it's not for sale.
One of the main holdups for the rights in America is apparently that you need to get three signatures on the contract, or the project dies. You need Naoko Takeuchi, you need Kodansha, and you need Toei. But Naoko allegedly doesn't like the changes that Toei made in adapting her work, so if she doesn't want to sign, then nobody can move forward without her.
The manga only needed two signatures, Naoko and Kodansha. And it was Kodansha USA who was doing the asking, and Naoko obviously likes her own original manga, and wants the world to experience it, so that got signed.
That's apparently why the new anime (as well as PGSM before it) claims to be more in line with Naoko's vision, because she's in charge now (now that she's not overworked drawing a regular series), and they need to keep her happy. The manga re-release was apparently the lead-up to the new series, and it would seem that they want all the attention to be focused on the new show, not distracted away by a BluRay release of the old one.