I think you are right that once someone has a commercial product...

I think you are right that once someone has a commercial product proven to work, the market is likely to gravitate towards that solution. The key is price point the product comes in at, and that's still a huge unknown for all 3 components (value of raw materials, cost to process and profit margin needed to recover all the R&D).

Lithium Carbonate prices are around US$10k/t and in LFP batteries you are needing around 0.8kg per kwh (with some 0.75 estimates also circulate as to figures higher than 0.8). Your 1kwh battery at ~US$50/kwh is using perhaps US$8 of lithium and $42 of other materials and manufacturing. If sold at that price any profit needs to be also factored in. A 60kwh battery on an EV might need ~50kg of LCE. The LCE to lithium metal multiplier is however 5.3x so some graphics circulating quote figures like 8-10kg of lithium in the battery.

Due to this 5.3x multiplier to pure metal, lack of pure metal industry scale and processing costs/profit margins the current price of lithium metal is around US$94-96k/t product. On long-run forecasts for LCE prices, lithium metal is probably nearer US$150k/t. You might have double-triple the density but if using products with a perhaps 10x higher price per kg, you can easily still end up with a higher price/kwh despite having improved density. This issue is likely to cascade through a lot of the componentry of solid state as I suspect they use high purity/high specification materials and processes.

If solid state didn't use high purity/high specification materials and processes, many of the probable thousands of scientists working on the issue would have cracked it years ago and there would be dozens of full-scale prototypes, pilot factories etc. I may be wrong, but I think solid state's heading for an excellent product that will capture the top/performance end of the market, take some of the middle market and make no progress on the lowest cost per kwh section of the market.