1.5 themes and 1.7 release. Will they work?

I am pretty much brand new to elgg and do wish to use it for my site. I am awaiting the 1.7 release before I consider going live because it looks like a few of the IE8 issues will be covered in the new release however, I am conncerned that my theme will not work with 1.7. When trying out 1.6 I noticed that very few 1.5 themes worked with it so I downgraded to 1.5. Will 1.5 themes work with 1.7?

Thanks in advanced!!