Nope. TP-Link has locked out OpenWRT. It's not a highly effective lock, but it is real and they actually deployed it as an update for existing hardware in the field and for new sales. They're not going to revert to the way things were and instead are trying to develop a new security strategy that clearly won't be feasible on the existing hardware that is now locked out.
And it's not like any router vendor ever actually actively supported third-party firmware; it's just a matter of how much DRM they use to interfere with it.
If you're saying that TP-Link has banned OpenWRT, I might quibble with your use of the word "ban," but I'd basically agree. (Maybe "block" would be better? I see that you yourself are shying away from saying that TP-Link actually "banned" anything, in favor of the phrase "locked out".)
Fortunately, the FCC might be backing down due to other sources of resistance and outcry. But that's not yet clear.
To which I would mostly agree, with an important caveat: TP-Link's violation actually had nothing to do with allowing third-party software like OpenWRT. Its own UI allowed end users to change region settings. This seems clearly problematic under the Commission's rules, even if the rules are vague in other respects.
So, on balance, I think this order sends an important signal that very well may be able to support things like OpenWRT without getting into trouble. But you're right that we don't know that for sure, given the language of the decree. All we know is that the FCC would really like it if the industry could figure out how to support OpenWRT, etc. without simultaneously making it easy to circumvent FCC rules.