Without going into the morbid and graphic detail, but speaking from hard and painfully learnt experience (altho gaining this experience involved most other major bones, organs, and joints in my body, it did not actually involve either of my hips - much to everyone's surprise, mine included!

) the bad news about
that ^ approach is that the longer you wait, the worst your hip joint/s will become and the greater the atrophy in all the muscles around it will be, resulting in a much greater likelihood of you ending up with issues/poor results after the surgery!
Sure, do the PT, work as hard as you can manage/bear on strengthening all the muscles around your hip as much as you can (maybe you'll be able to get a little fitter while you're doing it, cos that won't 'hurt' the surgery &/or your recovery!)
maybe even do the injections, but from my experience, I'd strongly suggest doing the injections
only if the Doctors firmly believe and can convince you that the injections will actually
benefit your hip/s, and
NOT just 'delay' needing to have the hip replacement done! Those injections can do more harm than good,
especially if you are going to need the replacement anyway!
So if the Doc thinks you're gonna need to get the replacement done anyway,
just DO IT - without waiting until you've let everything deteriorate so much that you've screwed your chances of ever getting a good result
AND put yourself thru a whole lot more pain and difficulty along the way!!
Just Sayin'