I've seen comments about sodium-ion cells getting down to US $10/KWh in the near future.
I think it is optimistic (to say the least) but if production rises I could imagine them at $25 - $35 per kwh for large systems in 3 years. This would be a game changer
If they could get them down to $10 - $15 per kwh for cells with limited cycle endurance then domestic seasonal storage is very interesting. Having a couple of MWh for £20K would be game changing for UK off-grid.