EQ7 is an awesome new upgrade from EQ6, with a lot of new features for designing, bringing in and using fabric images, etc. It's so good that many pattern designers are using it for new pattern designs and never actually doing the quilt top.
However, the EQ7 upgrade only works if you have EQ6 installed. You can get an upgrade from EQ5 to EQ7 but I think you have to go through the company to get it, I haven't seen it on any retail sites.
The only way to upgrade EQ4 to EQ7 would be to find all of the appropriate upgrade packs. I'm not sure if there was an upgrade from 4 to 5, but if there was, you might find one on ebay or someplace like that.
By the time you did that, you might be better off getting a good deal someplace on a new version and starting off fresh.
Here's a "back of box" image from our website that talks about the new features in EQ7:
http://www.quilt-kits-online.com/pro...eq6/eq7blg.jpg