LN can be a crucial element here: Lightning is a tool which is able to facilitate some purchases, and once it becomes established there could be a "domino effect", encouraging spending in a very similar way to what prepaid cards achieve. The coins you have locked one time on LN, are coins you'll be willing to spend eventually. Thus, businesses for the first time have a tool to measure the potential of the "Bitcoin as a currency"-economy. If this economy is growing, then there will be more businesses trying to enter that market, which means more people earn their money in BTC. And so on - the money could start to really circulate, instead of being mainly bought and sold at exchanges.
Interesting perspective. I do however wonder how long this will be a valid metric with how LN will eventually take over a lot use cases of the main-chain where it's still speculation that is the driving force behind this market.
Another thing is that you can't exactly know what people are doing on LN because it's not as transparent as the main-chain is, which I'm sure a lot of people (including myself) here would consider an extremely bullish development.
Overall, the volatile nature and the insane up side of Bitcoin are more of an obstacle in my opinion. Not many dare to accept even a portion of their wage in Bitcoin if you discard the few geeks working for crypto companies.