I think there is going to be a lot of interplay between a lot of factors for this to become a commercial reality.
The first thing is that the human brain tends to discount events further in the future - hence why politicians often implement positive law changes immediately, but negative law changes a few years in the future. With that in mind, consider:
1. Cars last for a median of 7 years. If batteries are lasting 80% to 7-10 years, the compelling reason to get longer lasting batteries is fairly marginal.
2. Technology keeps changing. Even if you had a battery that lasted forever, if it was significantly more expensive than a 7-10 year battery, who would commit to that if there's odds of a smaller, more powerful battery in the future?
So if you were presented with say, paying $10k for a storage system now, with the possibility of needing to replace it in 2027 with something that is likely to be cheaper and better then, or paying $15k for a solution that could last a lifetime, but might not even suitable for use in 10 years, which would you choose? And a 50% premium is pretty small.
3. From the manufacturer's point of view, they know this turns batteries from a consumable to a capital investment. This means that their customers go from buying regularly, to only buying it when they have a new application. They will need some pretty juicy margins to convince them to cannibalise their existing business to make this new battery.
Now, consider 3 together with 1 and 2. Some risk seeking company decides that even though the battery is only marginally more expensive, they figure that there is a market for everlasting batteries.
Scenario A - they market it as a premium. There is a market, but its very small. Even though the margin per unit is generous, the volume does not permit a good gross profit in relation to capital investment.
Scenario B - they take a loss leader to get volumes up - much like what Musk is doing with the Teslas. They may take first market share, they aren't making money out of it. They will also decimate the market, forcing competitors to cut margins on existing products or move to compete with this one.
You can't keep running a loss leader forever, so eventually the market will normalise. This could restore a healthy market, but the first mover basically will have spent money to only change the industry, not for its own profit.
Unless you can get billionaire sponsors like Elon Musk, or the government to sponsor this for idealogical motives, rather than profit motives, this will not get off the ground.
Unless a new technology is either cheaper, or substantially better in the SHORT term, it can be hard for that technology to succeed commercially.
