Here is my experience. Note I was on Mavericks, using iPhoto, with thousands of events sorted by date... The short story is after updating the Mac to Yosemite 10.10.3, updating the iPhoto Library using the new Photos app (which converts the iPhoto events to Photos albums), upgrading the phone to 8.3, and re-syncing the phone using iTunes - my photos and albums were in the correct order!! Yay!!
There is some devil in the details... Here are the details!
Process and Results
1. Backed up my iPhoto library (ya' never know...)
2. Upgraded iMac from Mavericks to Yosemite 10.10.3 (this also loaded new Photos app)
3. Opened new Photos app, and converted original iPhoto library (note I did NOT turn on new iCloud for sync - I want to use iTunes....)
Results when viewing pics in new Photos app:
a. All my events were converted to albums in a folder called "iPhoto Events" in the new Photos app.
b. The new albums created had the same name as the corresponding event, the same "key photo", and they were in the SAME order as the events were in the original iPhoto Library (mine were sorted by date). Pictures within the album were also in the SAME order as they were in iPhoto
c. Note that the "events" from iPhoto are now "albums" in Photos inside a folder. There does not appear to be a way to automatically sort albums by date in the new Photos app - it seems to be all manual sorting for albums and pics. But the conversion started them out in the same order as the iPhoto events/pics were originally
4. Upgraded iPhone iOS from 7.x to 8.3 via iTunes
a. Note - if you look at you photos on the phone immediately after the iOS update all the events are in random order (same problem this thread is about) but don't worry!!
5. Re-sync'd phone and photos using iTunes
a. Note I selected a subset of the albums within the "iPhoto Events" folder on the iPhone photos sync screen in iTunes)
6. Looked at photos on phone
Results:
a. Albums on phone were in the SAME order as they appeared on the iTunes Photos sync screen
b. For me, that meant the converted event albums were all in the same order as they were prior to these upgrades (yay!!)
Note that to control the order of albums on your phone, you need to get the albums in the order you want within the Mac Photos app first... then sync using iTunes to your phone. So if you import new photos, then create an album, put that album manually in Photos so the sequence of albums is how you want it to show on an iOS device. This applies not only to albums sequence, but also to the folder sequence (and the albums within them),and the sequence of pictures within an album.