Pressure to maintain revenue growth will lead them further down the path they've already been on for a while (long-time non-paid Duolingo user here): longer, more frequent, and more annoying ads, and more frequent upgrade calls-to-action. I swear there are some days when I'll do ten lessons and see the exact same upgrade ad after every single one.
It seems like a trap they dug for themselves: optimize the drilling process for engagement instead of speed of learning, maximize eyeballs, advertise -- and that sours me on the paid upgrade, because the drilling is such a grind. I'd happily pay if the instruction felt efficient.
