They've sort of stopped talking about it, and avoided the topic whenever people try bringing it up for a while, but WAAAY back in the day, there was talk about single player, and about a full campaign being a planned part of the release build. Realistically, if this "beta" was actually a beta, it SHOULD be feature-complete, but they're still adding game modes and have yet to include any real PvE even though such content had been promised. There are practise matches where you can fight bots, but the AI is pretty incompetent and the only way it's going to hold its own without massive overhauls on the system would be to give it "cheats" like buffed stats (turning the ships into damage sponges with bigger guns than you) or higher-tier ships than the players can fly.
According to the devs and Greybox, they've already "expanded" from 15 ships to "over 50". What's actually happened is that they've stripped chunks off the original 15 ships to make them crappier and less fun to fly and marketed that as a tier system.
Most people who have been around from the beginning are hoping they TAKE BACK the ships they "added" and sell the super-obvious reskins that don't even pretend to have remotely varied stats, but linear upgrades from tier to tier. Instead of having a failtastic attempt at tiering the game, they should have just the original 15 ships (with room to add more actually different and unique models) and sell the different tiered variants as skins for the base ships. Many of the modified designs are pretty awesome looking, and would be well worthy buying as cosmetic options.
None of this is particularly likely to happen, though, because the devs are incredibly slow to realise good ideas that they're being beaten over the head with. I'm not going to rule it out entirely, but it took them 6 months to admit the most blatantly provable part of the progression 2.0 mistake was a mistake. And that had been such a hugely obvious blunder that the few people who suggested it might happen were almost laughed out of the forums for thinking it was a plausible theory about the direction the game might be heading before we saw it come to life. Before 2.0 actually happened, nobody thought it was possible for anyone working on the project to be that obviously and obnoxiously stupid. Turned out, not only were they that stupid, but they were stupid enough to both implement the literally worst attempt the world has ever seen at an already-impressively-horrible game mechanic AND to double down and spend 6 months shutting down or shouting down every complaint they could find about it before finally admitting they were wrong (and openly describing it in terms that are censored on their own forums... go figure).
Where will they go from here? Honestly, I don't think even THEY know that. The earliest parts of the beta, and almost the entire alpha testing period, were a more fun, and more stable, experience than what you're getting now. I would hope they're going back where they came from, but I sincerely doubt it. I hope they can actually grow up enough to admit the game wasn't, and isn't, ready for beta, and turn back the clock. Given the nature of the business side of things, that's probably not going to happen, but it would be a bigger step in the right direction than even the announcement last month that they had screwed up with the maintenance system.
Step into your daydreams, and follow them home