Target Display Mode and HDMI?

At work I have a 2009 iMac with a Mini DisplayPort.

We're going to be getting new MacBook Pros with Thunderbolt and HDMI ports.

I'd like to set up the iMac as an external monitor using Target Display Mode. From what I've read, it looks like it doesn't work going from Thunderbolt to Mini DisplayPort.

Will it work from HDMI to Mini DisplayPort?

Thanks.