Updating app that has newer version than the store it was bought in I bought an app in the Samsung Play store, only to find out later that there is a newer version available in the Google play store.

In case the developer doesn't update the Samsung offered version, is there some way to update it using Google Play?   When I got to the app in Google Play it recognizes that I have the app installed and even offers to let me uninstall (but not upgrade) it.  If I try to uninstall it warns me that Google play didn't install it and asks if I really want to uninstall so I'm not sure what dangers might lie there.  If I go through with it, might I perhaps be able to re-install from the Google Play store and get the latest version, or might something get totally messed up?
No, you can't update it from Google Play. It would be like buying your phone from Carphone Warehouse and then expecting Phones4u to help you out with a problem just because they sell the same phone. Or buying a music download in Google Play and expecting to be able to download it from iTunes. You've paid Samsung for the app, not Google.

If you uninstall it via the button in Google Play, the app will just uninstall in the usual way. You'll be able to reinstall it from the Samsung App Store if you change your mind, but you still won't be able to download it from Google Play unless you buy it there.

Just wait a week or two to see if there's an update. Apps uploaded to Samsung's App Store have to be "certified", just like Apple's, so there is often a delay before a new version will appear there.