I don't envy him trying to wrap 9 books with a sizable gap in the middle of the series.
I thought legacy ended OK - its was the whole end state of the GA being brushed over that disappointed me most, but I agree after 9 books it should have been better.
I agree with your concerns but there's still a lot left to the series so I cannot begin to think about what Denning will need to wrap up, there's:
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Ben & Vestera
Abeloth (assuming she's kicking around)
Daala vs Jedi
Jacen's fall to the darkside
Tahiri (assuming she's not wrapped up by Conviction
Jaina & Jag
I think if Denning can stick to ending on two or three of the those issues, and the rest addressed in the previous books we will get a decent ending. I think if there are still a lot of loose ends like with legacy then we will be disappointed.