The quality of Sparrow is it's simplicity. Adding features to it would make it evolve in bloatware. See MS Word. They now reshuffle menues to justify upgrades. I guess in some next version, menues will be at the bottom of the window.
This is not a long term solution. The only viable solution was to reduce burn rate as close to zero as possible. This means producing a new software.
Developers publish feature lists for an upgrade cycle, users vote with their dollars, different features can be funded, etc etc? There are a couple of open source projects (like PostGIS) that have similar programs...