This thread is old, yet here's a quick update according to my experience:
Wildfire 5 can open native SolidWorks 2010 files. I set up the Windchill Workgroup Manager for SolidWorks and we ran all test cases we could think of. There are a few drawbacks, though:
1. They are imported as dumb solids, so if you want to be able to update SW geometry in WF5 then you are out of luck.
2. I had both SW and WF installed on my machine and I was able to use the models from SW into WF assemblies. It seems you need SW installed so you can integrate your files into WF assemblies
3. You can integrate assemblies as components in a larger WF assy, but just like .sldprt files, don't expect to be able to modify the geometry of their components.
4. There's no way SW 2010 can decently open a WF Family table
5. Exporting the assembly with the SW components will replace the SW parts and assemblies with WF files.
6. Export from Workspace is not available in the WWGM for SW so your only option to export the contents of your workspace is to pack and go from within SW.
...among other things.
I had the opportunity to participate in a beta testing of Creo 3 and you can expect little change on this part. The PTC guy mentioned that true Heterogeneous Design will come in a later datecode of Creo 3. The Beta we tested was not working with Windchill nor with the Work Group Manager for SolidWorks so I have no comments on this part. About the opening of SW files, they open, but still as dumb solids. I tried to open a decently sized native SW assembly (~ 1000 parts) in Creo 3 and it opened, exploded and overall worked fine the second time I tried (The first time it crashed, but it's a Beta so bugs are to be expected). I didn't see any major difference between the way they are open in WF5 and Creo 3, but my tests were not extensive. If all you need is to integrate common parts or libraries that won't change then you have a working solution here since WF5, but if you need to edit SW files directly in Creo then you, like me, will need to keep waiting.
I hope this information still is useful.