Ask HN: What should I choose to maximize both learning and earning?

Recently I read a news and my mentor also confirms it:

"There are a lot of arguments for jumping ship every few years. The economy isn’t what it used to be—and never will be again. Workers who stay with a company longer than two years are said to get paid 50% less, and job hoppers are believed to have a higher learning curve, be higher performers, and even to be more loyal, because they care about making a good impression in the short amount of time they know they’ll stay with each employer." [1]

I'm a Developer-turned-Manager in a Japanese startup. I have been working here for 40 months, but there're stuff about business to learn from my bosses and investors. However, the company is quite struggling (I'm being paid 20% below the market) and there're no seniors with higher technical skills than me.

What would I do to maximize both learning and earning: job-hopping after 2 years or staying till I'm the smartest guy in the room or anything else?

[1] http://www.fastcompany.com/3055035/the-future-of-work/you-should-plan-on-switching-jobs-every-three-years-for-the-rest-of-your-