Very much doubt Starc (fitness permitting) is being dropped, nor do I think he should be. What's he done wrong exactly? Had a middling summer but wasn't terrible, some important, match-changing spells at different times, and his record over the last two years is almost identical to Hazlewood, who is quite rightly considered a lock by most.
That's 103 wickets @ 24.92, SR 43.91 in 22 tests for Starc and 109 wickets @ 25.06, SR 54.51 in 28 tests for Haze since the start of 2015. If you make the period shorter it tends to look better for Starc unless you just look at the last 3-4 tests. Throw in Starc's batting, which is 582 runs @ 21.56 with 5 50s in the same period, and his case is even stronger.
Obviously Pattinson is in the mix but I can't see the case for him replacing Starc at all. Clearly between him and Cummins for the third seamer spot, which also makes a really balanced pace attack.
I feel like if Australia tour Bangladesh (it's still not clear to me if this is actually happening, or when) they should go with basically the same team as India but give Khawaja a chance in the subcontinent for someone, at least if he's shown anything at all in the preparation time, in the nets etc.
If the Ashes were to start without any cricket between now and then, I'd go with:
Renshaw
Warner
Khawaja
Smith
Handscomb
Maxwell
Wade
Cummins
Starc
Lyon
Hazlewood
And can't really see a strong case for any changes there. It's just overthinking things IMO. Marsh was a chance but I think his failure in the last test here probably means he'd need to play in Bangladesh and do very well to have a chance of being picked in the summer.
Pattinson obviously the next seamer in line, O'Keefe the spinner, batsman is a bit trickier because you've got some experienced backup but I can see them picking a young batsman instead if there was a vacancy. Cartwright, Lehmann, Patterson would all be a shot based on form.