Look at the decline of lutris in term of revenue (around 2020), it seems to be inversely correlated with the growth of competitor like heroic game launcher and playnite.

What you mentioned is one possible scenario, but the negative one is that lemmy userbase will continue to decline and there will be less feedback/income/contributions to keep the project going, the resources spent on basic development on sublinks and piefed could be used to make lemmy even better and developing experimental addons and gathering feedback on this kind of experimentation (e.g. in the form of surveys).

I am also not sure we are at a point where starting to experiment is the best option as features that seem to have more of a consensus are not yet implemented (e.g. multireddits, the issue with the most “thumbs up” on github).

With that said lemmy did manage to overcome previous open source competitors, If i would have to estimate probabilities like in the good judgement project i would say there is a 40 percent chance lemmy would decline and a 60% chance it will maintain its resources or grow.