It'll likely continue to happen organically: niche communities on reddit will keep getting fed up with the changes, and migrate to lemmy.
I don't know if we'll ever reach a tipping point, because redditors have shown that there's almost nothing they won't tolerate, but its also likely they still don't know that alternatives exist. There's a general conspiracy of silence about most fediverse software. Even with all this recent reddit drama, not a single article bothered to mention lemmy or other alternatives. The info is out there, but interested people have to go out of their way to find it.
We've also added a scaled sort to boost posts from smaller / less active communities, so that should help some with discovery. It'd also be nice for instances to use the sidebar, pinned posts, or site taglines to highlight smaller communities to help them grow.