Do most immigrants today have sufficient incentive to learn English?

Yes. Most jobs require that you speak English. Almost anywhere you go, the de facto language is English. Also, 83% percent of Americans speak English as their primary language (they speak it at home and outside of the home). Many people speak another language at home, but speak English at work/school/etc...Next time your out walking around, read everything you see (signs, posters, etc)... almost all of it will be in English.