I know these are back-of-the envelope calculations, but on the first part, this seems wrong. "A few thousand bitcoin users from /r/Bitcoin" upgrading to Segwit might have very little effect. We have no idea the weight of their transactions nor whether any given thousand redditors transacts much if at all. (HODL!)
The latter part (exchanges) is what matters: economically relevant nodes. The majority of blockchain activity comes from exchanges and services, not regular users. My feeling is that exchanges are far more concerned with scaling their infrastructure due to user growth that they can't handle. And I support that. As a customer of several exchanges and brokers, I can say that performance/trade engine/API/downtime issues are a million times more important to me than withdrawal fees.
Segwit was touted as an opt-in upgrade. Threatening to leave an exchange I otherwise like over it? That's absurd.
