I like the way this new function doesn't automatically save the pic, from iMessage, IF you want a quick (no keep pic) to send.
I do understand the usefulness of the Autosave feature we used to have, But I think they have included this concern in the Camera option within iMessage:
If you want your iMessage pictures to be automatically saved to your iDevice Camera Roll, follow this process:
1) Click the Camera icon, within iMessage, to access the live camera and your recent photos,
2) Swipe Right to access the Camera and photo Library,
3) click Camera, (now you are in the actual Camera App, and all pics are saved from here,
4) Take your Pic, edit/touch up if you want, then save, or don't save, then click Done.
5) this picture has now been put into your iMessage text box ready to send, Send it or Delete it.
Note: This is based on iPhone 6s+ running ios 10.0.2(14a456)
I think Apple has simply added a few new options that are more efficient than using the Camera App hand over and hand back, but as you can see above, the old functionality is still there.
Chris G.