It is still very, very low, yes. A large part of the reason for that is online poker is still in its embryonic state in Russia and the Russian language infrastructure for online poker is just being built as we speak. Right now, with online poker, Russia is about where we were in 2001 and since the word has absolutely no utility whatsoever beyond this one particular niche, there is little "chatter" to speak of, beyond a few forward thinking sites that are already targeting that particular market.
Historically, when you examine the trajectory of how Online Poker has saturated, it's generally exponential. Here's "rakeback" English from 2004-present- as you can see, it went from zero to highly relevant once critical mass hit.
The handful of Russians seeking Rakeback at present do seem to be using it as a stand-alone term; In Yandex, it is being commingled with English language names of poker sites:
However at present, "Rakeback" English still trumps "Рейкбэк" in yandex by an almost 3/1 margin, but it's all still very speculative since the volume for either is below 1K. That said, as a poker player with boots on the ground who see's what's going on, I have faith in this one.