Sodium batteries technology will never catch up lithium...

Sodium batteries technology will never catch up lithium batteries. Any technology you develop with sodium will yield a lighter (less weight) and higher density equivalent with lithium. Just substitute the sodium ion by lithium in the battery (take a look at a chemical table).
Sodium batteries are just a cheaper and less performant equivalent to lithium ones. They will have their niche if lithium prices go to the moon again, but not because they will perform better than lithium. Only because they would give more profits to car sellers.
Try to do a research about how many inventions, patents and research papers you find for lithium batteries and how many for sodium ones. Technology between both chemicals won't narrow, just the contrary. More gradual ups and downs are typical of maturing markets, which is what we all expect with lithium. Not because of new technologies. We just need lithium supply-demand chains to be more equilibrated (on both directions).