- scaling issues (it can't be used as a currency if this isn't fixed) - power issues (would be nice if we didn't create a huge pointless energy sink if we could avoid it) - the amount of footguns in ethereum (I think the language is too permissive)
It looks like this solves at least 2 of the three!
The other part, which is on Ethereum mainnet already, is a layer-2 idea called rollups, which store transactions on chain in a very compressed format without losing security guarantees. There are several rollup systems, capable on today's Ethereum of doing 1000 to 9000 simple tx/sec.
Once both systems are live, total capacity will be 20K to 100K tx/sec, not counting the quadratic improvements.
On the research side, there's also work to make data validation more efficient by replacing merkle trees with something more compact, like polynomial commitments. That would add another 10X factor to rollup scaling.
Regarding footguns, people are working on more rigorous languages than Solidity that still compile to the EVM. So far their compilers aren't as solid so they don't get much production use yet.
Anything more than ~3000 tx/sec will be a game changer and maybe ethereum will finally deliver on the promise of usability as currency.