It certainly won’t be empty but with the 16:44 before and 17:45 following it, the latter in effect an additional train, and only going as far as Moreton, I doubt it’ll be too packed.
A little like the opposite Turbo arrival in the morning which usually has a few seats free.
If someone finishes work at 5pm in central Oxford, then they are not able to get the 16.44 and won't want to wait for the 17.45, so they will continue to do what they do now and get on the 17.2x departure.
As far as I can see, GWR's attitude is that even though the two-car Turbo is odds-on to be full and standing on departure from Oxford, given the growth in custom at Hanborough in particular, 50 or 60 people will get off there 10 minutes later, so that will somehow 'fix' the problem. And they are not going to provide a three-car 165, even though they now have a solution available to the old issue of Turbos not having selective door controls, which made operating the afternoon halts service so troublesome for so many years.
This despite the fact that anyone can see the sheer number of people on the platform at Oxford waiting to board the the current 17.25 departure (precious few of whom are going to stations beyond Moreton-in-Marsh, so removal of Worcestershire passengers from this service won't make much difference to numbers). And there will inevitably be people who continue to want a 16.20ish departure off Paddington (or have an off-peak ticket) and will be changing at Oxford for the halts train, rather than rushing for the 15.50, or delaying their departure until 16.58 - which is a peak train for ticketing purposes out of Paddington.
It also remains to be seen what people will make of the morning hals service running about 15 minutes later than it has for many years, to even out the intervals between trains heading to Oxford. Some people who start work in Oxford at 8.30 must be hoping they have understanding employers, as an 8.25 arrival removes their current walking time to places in the heart of the city.