It looks like the three dots (and bottom buttons) are not completely gone, at least, depending on the app. I'm okay with the hamburger if it's more a top level mode change (like from Inbox to Sent Items or something like that), while the bottom stays with the functions (new email, select, etc). And LLPO was right....it was a pretty elegant solution for the captions, as well as showing common functions and allowing for more.
Showing concern is good, voicing it is great (Microsoft seems to at least listen to users), but I believe it's premature to assume the WP8/8.1 design (which I'm still in love with) is completely dead and gone and that the 10 UI is horrible. Give it a couple weeks, test the 10 DP, and let them update it, test it again. Something tells me it will still be beautiful and functional.