I also think that Thunderbird's position can no longer qualify for the adjective 'huge' when coupled with community value, it is well below 1% of the market.
After using it for years I gave up because the bugs were no longer fixed timely, the performance simply terrible and the upgrades were just as likely to cause you trouble as they were to fix something.
Rust has the future, I'm pretty convinced about that. It will take a very long time to materialize, but let's be honest here: without FireFox Rust would have never even seen the light of day, it only exists because a large amount of money earmarked for FireFox was diverted into developing Rust which led to further diminished marketshare for FireFox. The breaking change around plug-ins was another big negative in the near past.
Each represents a huge value to the community.
New and untried consumer products? Well, maybe. You never know which could be a big hit.
Still it's not obvious how to make money on any of these :(