I think you need to look at what your vehicle needs may be 5 to 7 years in the future, which is when (on average, not mustachian levels of driving) you'll hit that 100k mark.
The only thing more important to the average used car buyer than mileage is age. A car that's 3 years old with 100k miles is, cosmetically, going to look pretty great, minus the expected rock chips and scratches from extensive highway driving. The interior is also going to be in very good condition and will be more up-to-date than a 10 year old used car. The 10 year old used car will inevitably have more cosmetic blemishes and faults in the interior.
By this, I mean, it might be mostly a moot point whether you sell it before or after 100k miles. Or whether you sell it near 200k miles.
A quick KBB exploration (not exactly the scenario you'd be in):
A 2015 Subaru Outback with 95k miles is estimated to sell private party (in my area) for $10,950
An identical 2014 Outback with 105k miles is estimated to sell private party for $10,050
A similarly spec'd 2010 Outback with 195k miles is estimated to sell private party for $4,650
If you average 10k miles a year, $900 in additional depreciation costs is not a bad deal. If you don't expect major repairs (although, it is a Subaru) then holding it for another 5 years isn't so bad, either.
So that gets me back to my original point - your car will hold some measure of value for a long time assuming you can keep it looking decent and keep it running. Will it serve your needs in 5 years? 10? If it likely will, I wouldn't even worry about selling it at any point in the future.