Put ~8K miles on the Q7 TDI since acquiring it last October. Mostly highway miles.
Other than a few door handle sensors going bad, no issues and everything works great.
My dieselgate powertrain warranty times-out in mid June. I presently have 68K on the odo.

No CELs and no powertrain errors in VCDS.
Will pull the underside panels and look for oil leaks (there were none in Oct).
Anything else I should examine for potential warranty coverage before it expires???

 

That's a tough one really, as with such low miles on a TDI motor and the tranny you wouldn't expect there to be anything obviously going wrong with it yet, as all the 'normal' oil changes and general services were no doubt performed on it (except for the driveline...diffs/xfer case/trans fluid/power steering fluid; none of those have been touched by Audi, and you're past due on all those fluid services if haven't done them yet).

That said, the TDI's that have sat around a lot, or simply not driven much, or were buy-back cars during the dieselgate debacle that got stored for few years, those often will turn up with early HPFP failures or SCR system issues related to long-term inactivity. DPF fluid also has a short shelf-life, etc.

Overall, all you can really do is proactively scan the car via VAGCOM looking for faults that haven't or won't pop the CEL, and regularly verify the oil & coolant levels. If there's no oil leaks on exterior of the block/valve covers now or from the rear main seal (drips/seeps from the weep hole/wires pass-through at bottom of bell housing), then that's not likely to change in next couple of months, so just recheck closer to drop-off date of the warranty. It is worthwhile to ask your Audi dealer to verify the exact ending date for your TDI warranty, as mine turned out to be several months later than I believed it was based on our purchase date and the documentation online suggested.

FWIW:
Our '15 TDI dropped off the settlement warranty after hitting 120k miles, and I didn't think we were gonna get much out of it on that car. Going into the home stretch it'd only had a few sensors swapped out on it...and O2 and a NOx sensor, etc. Also ended up getting the coolant leak in the engine valley around 116k miles, so did end up getting some 'big labor' hours repair done by the warranty, and since the Audi dealer only did the oil cooler seals the first time, they got to go back and do it all over again to replace the leaking coolant valve for the cylinder cooling circuit, which is what feeds the EGR Cooler and Oil Cooler, as well as the cylinder head. They fought me really hard on that repair claiming it wasn't a covered item, although that was pretty standard response at every dealership I've been to. Even my escalation to Audi USA was rejected; but I proved them wrong, and got that overturned.

 

Probably worth peering between the pleats of the fuel, engine oil and gearbox filters.

Electric handbrake fitted? Included in warranty? Is it noisy?

Free play or split dust shields on drive/prop shafts.

Leaks on cylinder heads above exhaust manifolds on diesel cars.

Can dpf health be ascertained through diagnostic software?

Best to flag tons of issues where the evidence of an issue is weak because if the thing breaks a month later you have a record.

 

Definitely check both valve covers and injector insert/seals. I've just had them done on two 15 q7s that were due to come out this month. Both got the valve covers replaced with new, the injectors pulled and seals changed, couple breather hoses etc. One of them has been troubling the dealership for about a month. Injector #1 started throwing flow codes after the changes, and has led to an intake replacement, possibly all six injectors being replaced. Unsure what the final outcome will be, as they are still trying to get to the bottom of things.