Adobe makes money with tools, not with Flash. If Adobe makes good HTML5/JavaScript tools, and keeps making Photoshop, they'll be fine.
But, I agree with you that if they pivot they should be fine. To some extent they're also (smartly) re-purposing their existing tools for native mobile development: http://labs.adobe.com/technologies/packagerforiphone/
I'm skeptical that they'll be big in the "good HTML5/JavaScript tools" business based on what they have[n't] done with Dreamweaver, HomeSite, ColdFusion, etc. They just don't seem to have a lot of developer momentum there, IMHO.
If seems like if Adobe plays their cards right, they end up making a lot more money, although they become a lot less prominent brand.