Nope, the modules are not forward or backward compatible.  

Eon tends to fix Vue Infinite first, then take those fixes and put them into the other products.  Therefore, Vue 6 Pro, Esprite, and Easel tend to not have as many bugs - we have located them and stomped them out of existence...  The last set of bugs have mostly to do with Poser imports.  If that is not a concern for you, then I would go ahead with the upgrade.  Otherwise, I'd say maybe wait a week or two at the most. 

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