JSPM-the only package manager suited for HTTP/2
Do you love your webpack pipeline? Or your Browserify pipeline? Were they hard to setup? No probably not that much. But you are proud of them. You should not be. They are in the end a hack.
As @MattWilcox summarized in his excellent write-up, concatenation of sources or bundling is harmful in the web of tomorrow.
Nginx should get HTTP/2 support in the 1.9 milestone, which is due in 9 months. 9 months is not that much considering how long most web apps are in development.
So do you want to be as fast as possible when the web gets HTTP/2? Use JSPM. It might not currently be as popular as other/older solutions, but it will certainly be quite important in the long run.