The HAVOC concept for exploring Venus with airships has been made public almost three years ago now, but the scientific publication seems to never have been cited, neither am I aware of any official information about a follow-up study. Is the concept currently completely out of focus of NASA or is it being developed further?
The project is likely abandoned without any followup in a similar vein, drawing from multiple sources.
Official project page
NASA's page for the project states explicitly:
This project is no longer active.
The page seems to be up reasonably to date:
Page Last Modified: December 13, 2018
NASA Report on inflatable technology
The [HAVOC] study led to a proof of concept model and analysis work, but was not funded for further development
Searching NASA technical reports
Searching NASA Technical Reports for HAVOC shows only unrelated reports.
This article verifies NASA's continued interest in possibly doing the HAVOC concept sometime in the future - however it evidently is not yet at the top of their priority list, because, in so many like-words from naturalnews.com:
"NASA has yet to release any dates for the concept to start."
Thus, the short answer to your question is that the idea exists inside the NASA, but currently they don't do anything to reach it, and it is unknown, if there will be a positive change ever.
To objectively examine the future possibilities, we have to understand the decision making structures of the NASA:
Decision making is a formal process in systems engineering that takes the outcomes of the opportunity structures and makes formal agreements on the system design or system operations. There are several aspects of decision making structures the systems engineer should be cognizant and then provide input to project management to ensure an efficient information flow and limit the uncertainty in the decision-making process. Information theory provides the mathematical basis for structuring decision boards. The overlap of delegated board scopes can lead to uncertainty in the decision process and is an aspect that the systems engineer should ensure is properly structured.
What we can see here:
- There is a balanced, but also very bureocratic structure of different groups.
- Engineering arguments have an above average effect to the decisions.
Currently, 3 terraforming targets exist in the foreseeable future: the Moon, the Mars and the Venus. As we can see in the news, currently the Mars is clearly the winner, however we have no clear timeline even from the Martian colonization. Their advantages might be not so evident in the actual decision-making, particularly if we comparise to the pro-Venus arguments:
Both the Moon and the Mars do not have enough of a diameter to produce sufficient gravity to hold onto any terraforming attempts of producing oxygen there, at least not on a geological timescale. It might be enough for our life, or in the predicted survival timeline of our civilization (some tens of millions years), but beside this, there are also other problems.
On Mars you weigh 0.38 your weight on Earth, and we’re not entirely sure what this would do to human health. To keep Mars residents’ bones from demineralizing, for instance, they might need to exercise inside large centrifuges every single day. Thus far, NASA and other organizations have studied effects of partial gravity to a limited extent on humans by producing Mars and lunar gravity for short periods (under a minute) during parabolic flight.
If no solution for this problem, and for the problem of the escaping atmosphere is found, then Venus remains is the only choice. For pragmatic reasons of terraforming, since its gravity is approximately the same as Earth's.
Once we have dirigibles safely orbiting just 37 miles above hot Venetian ground - the scientist onboard will not be able to resist quickly coming up with ideas on how to moderate the ground temperatures.
Then having maybe robots clean up some of the sulfuric acid in the Venetian soil. While at the same time working on ideas to introduce 21% oxygen to the ground atmosphere. Then in the dirigible labs working on new genetic strains of plants that resist any left over sulfuric acid that the robots could not completely eliminate. Once all of that has been attained - the dirigibles of Venus will probably historically be recorded as the second MayFlowers to another world.