LR4 with CS5/ACR

Apologies if this is a dumb newbie question.

I almost always use RAW files from a Canon 40D (or even my old Rebel 300D). After years of using ACR and CS3, I recently upgraded to CS5 and LR3. I have not really spent much time with LR3, but I thought I would give it a try.

Because I just recently purchased LR3, I got the word from Adobe that I can have a free upgrade to LR4.

My question is, will LR4 work well with CS5 and ACR, or do I have to also upgrade something with them? Can I have both LR3 and LR4 on my computer (but not running them concurrently) or is it better to uninstall LR3 first?

Thanks.

First, Adobe has put out a "Release Candidate" for Camera Raw 6.7 for CS5 that is fully compatible with Lightroom 4:

http://labs.adobe.com/​downloads/cameraraw6-7.html

Second, you can use LR 3 and LR 4 at the same time, and you can use CS5, but the LR4 processing will be "different" from the LR3 processing and there will be the same differences between LR3 processing and ACR 6.7 processing. However, once you process your Raw files, if you want to Edit in Photoshop then the Raw data is converted into images and PS doesn't care about the Raw anymore, so you can edit from LR3, LR4 or ACR7 and PS will be happy whatever.