The problem with your idea is that it would cost just as much to boost the orbit as it would to deorbit it, then you'd have to launch a Shuttle mission at the cost of several hundred million dollars. Not only that, but if you boost it over about 300 NM high, the Shuttle couldn't reach it, so you'd have to wait until the orbit decayed enough. By that time, the Shuttle may no longer be operational. I keep saying the Shuttle because nothing I've read about the CEV indicates it will have the ability to return large payloads to the Earth. The Hubble is large - about the size of a city bus. I saw it at a Lockheed facility in 1988.

I really don't think there's a need to launch a deorbit mission. The Hubble is in a 28 degree inclination orbit, so it doesn't pass over that many inhabited places. They could do the same thing with the Hubble that they did with Skylab (which, if memory serves, also lacked a propulsion system) - when the perigee was low enough, they turned Skylab perpendicular to the line of flight to increase drag. That caused it to deorbit successfully with only a few pieces reaching the ground in Australia.